Wound dressing and method of treatment

ABSTRACT

A wound dressing, a method of manufacturing a wound dressing, and a method of treating a patient are disclosed. The wound dressing may include an absorbent layer for absorbing wound exudate; and an obscuring element for at least partially obscuring a view of wound exudate absorbed by the absorbent layer in use.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/219,886, filed on Jul. 26, 2016, which is a continuation of U.S.application Ser. No. 14/232,607, having a 371(c) date of May 21, 2014,which is a U.S. National Phase of the PCT International Application No.PCT/GB2012/000587, filed on Jul. 12, 2012, which claims priority to UKApplication Nos. 1112084.7 and 1211171.2, filed on Jul. 14, 2011 andJun. 22, 2012, respectively.

Some embodiments of the present disclosure relate to a wound dressingand a method of treatment. In particular, but not exclusively, thepresent disclosure relates to an apparatus and method for providingprotection at a wound site, for absorbing wound exudate, and providing anumber of benefits to both users and those around them over knowntechniques.

Patients have to live with chronic or acute wounds for durations rangingfrom a number of days to a number of years. Their quality of life isunavoidably affected, and even more so if the impact of the wound onpatients' daily activities cannot be minimised by the dressing chosen.

Patients often report fear of the dressing leaking, of odour from thewound incommoding their relatives, or of the dressing becoming unsightlyas it is being used. As patients move, the dressing may be submitted tostretching and/or bending of the skin, or rubbing from clothes or bedlinen. While modern dressings are designed to stretch to some extent,lifting of the dressing borders during everyday activities does occur,and reinforces concerns about leakage and odour. The corresponding worryabout stigma, and cleanliness, can limit a patient's activities in a waythat is not beneficial to their overall healing.

In addition, when patients are mobile, fear of damaging their woundfurther through painful knocks is also present.

The every-day life of patients with a wound can be seen as a balance ofrisks and benefits. The decisions taken by patients can sometimes goagainst the prescribed treatment or behaviour recommended by clinicians.Addressing some of the patients' concerns about the state of theirdressing while they are wearing it could help to steer patient decisionstowards concording with the clinician's recommendations.

In summary, the above-mentioned problems have heretofore been approachedin the following ways:

Prevention of leaks: wound dressing have resorted to the use ofsuperabsorbers in their construction to try to limit leakage of woundexudates out of the dressing pad. EP1156838 describes a wound dressingwhich combines a foam layer and an absorbent layer in intimate contactwith the foam, and capable of draining the foam. EP0758219 describes amethod for producing such an article.

Odour: several odour control dressings exist, including either activatedcharcoal layers (Carboflex®, Askina Carbosorb®, Sorbsan plus Carbon®,Carbonet®, Lyofoam C®) or cyclodextrins embedded into a hydrocolloid(ExuDerm Odorshield®, Avery Dennison). Where activated charcoal is used,it is most often placed behind a barrier layer, the intent of which isto keep the charcoal as dry as possible to enable it to trap odours.U.S. Pat. No. 6,348,423 describes an odour-control absorbent dressing,which contains a barrier layer between the wound side of the pad and itsodour layer. GB2420286 describes the use of activated charcoal tocontrol wound odour. WO0209782 describes the use of cyclodextrinsincorporated into a non-adhering wound dressing. No adhering absorbentdressing also containing a means of controlling odour is currentlyavailable on the market.

Conformability and movement: some dressings have been designed to bemore conformable to the body than a standard square shape. This is thecase for example of dressings design especially for the heel area, orfor the sacrum area. WO2008/149107 describes a sacrum dressing withpreferential folding lines. In such dressings, both the border and thepad of the dressing can be shaped in relationship to the particular areaof the body targeted. WO2004/047695 describes a dressing withindentation in its pad in a honeycomb pattern. Further related patentapplications describe other beneficial formats of indentations. Anexisting product, Comfeel Plus® by Coloplast, has a shaped border whichis claimed to increase adhesion and conformability. Furthermore,EP0902672 describes a conformable dressing which has a permanent setafter application.

Appearance and cleanliness do not seem to be addressed by existingproduct offerings, or to have been considered an issue for the patientin the published literature.

Protection from shocks and pressure relief: This problem seems to havebeen tackled in the industry in the light of preventing pressure ulcersfrom developing or worsening. It is generally accepted that structurescontaining air bubbles or gel parts will be able to absorb some of theenergy put into compressing a dressing, until the force applied leads tothe collapse of the dressing thickness. Foam dressings have thereforebeen used as part of a pressure relief protocol in clinical settings,but in conjunction with other methods.

WO2007/075379 describes a bi-component dressing, where a first part isformed as a wall around the circumference of the wound, and a second,flatter part, is placed on top of the wall. Pressure applied over awider area than that delimited by the wall, such as under a compressionbandage, would be mostly taken up by the shield structure.

WO2006/091735 and US2009/0069737 describe a similar concept, where alayer of material is punctured. EP1164995 builds on this idea, where apressure-relieving structure surrounds an absorbent part of thedressing, and is in contact with the skin.

WO2011/144888 describes the use of a three-dimensional knit within adressing.

The inventors have not found a structure described that meets more thanone of the patient needs outlined above. However, patient satisfactionwith a particular treatment, and therefore the likelihood that they willcomply with it, depends on several clinical and social factors.

According to a first aspect of the present disclosure, there is provideda wound dressing for providing protection at a wound site, comprising:

-   -   an absorbent layer for absorbing wound exudate; and    -   an obscuring element for at least partially obscuring a view of        wound exudate absorbed by the absorbent layer in use.

According to a second aspect of the present disclosure, there isprovided a method of manufacturing a wound dressing, comprising:

-   -   providing an absorbent layer for absorbing wound exudate; and    -   providing an obscuring element for at least partially obscuring        a view of wound exudate absorbed by the absorbent layer in use.

According to a third aspect of the present disclosure, there is provideda wound dressing for providing protection at a wound site, comprising:

-   -   an absorbent layer for absorbing wound exudate; and    -   a shielding layer provided over the absorbent layer, and further        from a wound-facing side of the wound dressing than the        absorbent layer.

According to a fourth aspect of the present disclosure, there isprovided a method of manufacturing a wound dressing, comprising:

-   -   providing an absorbent layer for absorbing wound exudate; and    -   providing a shielding layer over the absorbent layer, and        further from a wound-facing side of the wound dressing than the        absorbent layer.

According to a fifth aspect of the present disclosure, there is provideda wound dressing for providing protection at a wound site, comprising:

-   -   a shielding layer for spreading pressure applied to the wound        dressing over an area larger than the area where the pressure is        applied; and    -   a cover layer provided adjacent to and over the shielding layer,        on a non-wound facing side of the wound dressing.

According to a sixth aspect of the present disclosure, there is provideda method of manufacturing a wound dressing, comprising

-   -   providing a shielding layer for spreading pressure applied to        the wound dressing over an area larger than the area where the        pressure is applied; and    -   providing a cover layer provided adjacent to and over the        shielding layer, on a non-wound facing side of the wound        dressing.

According to a seventh aspect of the present disclosure, there isprovided a wound dressing, comprising:

-   -   an absorbent layer for absorbing wound exudate;    -   a fluid transmission layer; and    -   an odour controlling element between or in the fluid        transmission layer and the absorbent layer.

According to an eighth aspect of the present disclosure, there isprovided a method of manufacturing a wound dressing, comprising

-   -   providing an absorbent layer for absorbing wound exudate;    -   providing a fluid transmission layer; and    -   providing an odour controlling element between or in the fluid        transmission layer and the absorbent layer.

According to a ninth aspect of the present disclosure, there is provideda wound dressing, comprising: an odour control material and at least oneof a foam, an absorbent layer and a shielding layer, wherein the odourcontrol material is incorporated into the at least one other material.

According to a tenth aspect of the present disclosure, there is provideda method of manufacturing a wound dressing, comprising providing anodour control material and at least one of a foam, an absorbent layerand a shielding layer, wherein the odour control material isincorporated into the at least one other material.

According to an eleventh aspect of the present disclosure, there isprovided a wound dressing, comprising:

-   -   an absorbent layer for absorbing wound exudate,    -   wherein the dressing is shaped to include sub-areas, wherein the        dressing has rotational symmetry, and the sub areas define areas        of the dressing that are formable in different directions with        respect to each other.

According to a twelfth aspect of the present disclosure, there isprovided a method of manufacturing a wound dressing comprising

-   -   providing an absorbent layer for absorbing wound exudate,    -   and shaping the dressing to include sub-areas, wherein the        dressing has rotational symmetry, and the sub areas define areas        of the dressing that are formable in different directions with        respect to each other.

Certain embodiments of the present disclosure provide the advantage thata wound dressing is provided that has a reduced aesthetic impact forusers (compared to known dressings) yet allows clinicians to examine andvisually assess the wound area, such as assessing presence of blood,infection by-products and/or the extent of exudate spread across thedressing.

Certain embodiments of the present disclosure provide the advantage thata wound dressing is provided that has improved conformability to an areaof a patient to which it is attached, particularly for areas that arenot flat/planar.

Certain embodiments of the present disclosure provide the advantage thata wound dressing is provided that has improved performance in terms ofprotecting a user from shocks or pressure.

Certain embodiments of the present disclosure provide the advantage thatodour from a wound is controlled.

Some embodiments provide the advantage that the wound dressing can beused to collect wound exudate generated during a negative pressuretherapy process. A pump remote from the wound dressing or supportedthereby can be connected to the wound dressing and reused (or can bedisposable) whilst the wound dressing itself is used to collect woundexudate and may then be disposed of after use. The pump or other sourceof negative pressure can be connected to the wound dressing through aflexible tubing or conduit. In this arrangement, negative pressure candraw wound exudate and other fluids or secretions away from the woundsite.

Any of the embodiments disclosed herein are suitable for use with and,hence, can be used with a negative pressure wound therapy system to aidin wound closure and healing in which wound exudate drawn from a woundsite during the therapy is collected and stored in a wound dressingand/or in a collection canister.

It is the aim of certain wound dressing embodiments disclosed herein tohave an increased capacity for absorbing wound exudate reducing thefrequency with which the dressings must be changed. It is further an aimof certain wound dressing embodiments disclosed herein to manage themovement of wound exudate through a dressing to avoid blockagesoccurring that lead to reduced life of the dressing.

It is an aim of certain wound dressing embodiments of the presentdisclosure to provide a wound dressing having an increased capacity toabsorb compressive forces exerted on the wound dressing.

It is an aim of certain wound dressing embodiments disclosed herein toprovide a wound dressing having an increased capacity to prevent shearforces from an outer surface of a wound dressing from being translatedinto corresponding shear forces at a wound site.

It is an aim of certain wound dressing embodiments disclosed herein toprovide a wound dressing which can “give” in a direction perpendicularto and parallel to a wound site surface even when the dressingexperiences negative pressure.

It is an aim of certain wound dressing embodiments disclosed herein toprovide a wound dressing able to be used with topical negative pressuretherapy which helps maintain an open flow path so that therapy can becontinued unhindered by blockages caused by build-up of solid matter.

It is an aim of certain wound dressing embodiments disclosed herein toprovide a method and apparatus for treating a wound with topicalnegative pressure therapy by preventing blockage of a flowpath region ofa wound dressing.

Some embodiments disclosed herein are directed toward the treatment ofwounds with negative pressure wound therapy. In particular, any of thedressing embodiments disclosed herein can be used for absorbing andstoring wound exudate in conjunction with a pump, for example aminiaturized pump. Any of the wound dressing embodiments disclosedherein can further comprise a transmission layer configured to transmitwound exudates to an absorbent layer disposed in the wound dressing.Additionally, any of the wound dressing embodiments disclosed herein canbe adapted to provide for a port or other fluidic connector configuredto retain wound exudate within the wound dressing while transmittingnegative pressure to the wound dressing, though such a feature is notrequired.

According to an embodiment of the present disclosure there is provided awound treatment apparatus comprising: a wound dressing comprising:

-   -   any of the dressing embodiments disclosed herein;    -   a pump; and    -   a suction port for applying negative pressure to the wound        dressing for the application of topical negative pressure at a        wound site, the suction port comprising:        -   a connector portion for connecting the suction port to the            pump;        -   a sealing surface for sealing the suction port to the cover            layer of the wound dressing; and        -   a liquid impermeable gas permeable filter element arranged            to prevent a liquid from entering the connector portion.

According to another embodiment of the present disclosure there isprovided a method for the treatment of a wound comprising:

-   -   providing a wound dressing comprising any of the features or        combination of features of any of the dressing embodiments        disclosed herein, and/or:        -   a transmission layer comprising a 3D knitted or fabric            material;        -   an absorbent layer for absorbing wound exudate, the            absorbent layer overlying the transmission layer;        -   a cover layer overlying the absorbent layer and comprising            an orifice, wherein the cover layer is moisture vapor            permeable;    -   positioning the dressing over a wound site to form a sealed        cavity over the wound site; and    -   applying negative pressure to the wound site to draw fluid        through the transmission layer into the absorbent layer.

According to another embodiment of the present disclosure there isprovided a wound dressing for providing protection at a wound site,comprising any of the features or combination of features of any of thedressing embodiments disclosed herein, and/or:

-   -   a transmission layer comprising a first surface and a further        surface spaced apart from the first surface by a relax distance        in a relaxed mode of operation; and    -   a plurality of spacer elements extending between the first and        further surfaces and, in a forced mode of operation, locatable        whereby the first and further surfaces are spaced apart by a        compression distance less than the relax distance.

According to another embodiment of the present disclosure there isprovided a method for providing protection at a wound site, comprising:

-   -   locating a wound dressing comprising any of the components or        features of any of the wound dressing embodiments disclosed        herein, and/or a transmission layer over a wound site; and    -   responsive to a force on the wound dressing, displacing a        plurality of spacer elements extending between a first surface        and a further surface of the transmission layer whereby;    -   a distance between the first and further surfaces is reduced as        the spacer elements are displaced.

According to another embodiment of the present disclosure there isprovided an apparatus for dressing a wound for the application oftopical negative pressure at a wound site, comprising a wound dressingcomprising any of the components or features of any of the wounddressing embodiments disclosed herein, and/or:

-   -   a liquid and gas permeable transmission layer;    -   an absorbent layer for absorbing wound exudate, the absorbent        layer overlying the transmission layer;    -   a gas impermeable cover layer overlying the absorbent layer and        comprising a first orifice, wherein the cover layer is moisture        vapor permeable.

According to a further embodiment of the present disclosure there isprovided a method of applying TNP at a wound site, comprising:

-   -   applying negative pressure at an orifice of a cover layer of any        wound dressing embodiment disclosed herein, a peripheral region        around the wound site being sealed with the wound dressing, such        that air and wound exudate are drawn towards the orifice;    -   collecting wound exudate, drawn from the wound site, through a        transmission layer of the wound dressing, in an absorbent layer        of the wound dressing; and    -   transpiring a water component of the wound exudate collected in        the absorbent layer through the cover layer of the wound        dressing.

According to an additional embodiment of the present disclosure there isprovided apparatus for dressing a wound for the application of topicalnegative pressure at a wound site, comprising a wound dressingcomprising any of the components or features of any wound dressingembodiment disclosed herein, and/or:

-   -   a liquid and gas permeable transmission layer;    -   an absorbent layer for absorbing wound exudate;    -   a gas impermeable cover layer overlying the absorbent layer and        the transmission layer, the cover layer comprising an orifice        connected to the transmission layer; and    -   at least one element configured to reduce the rate at which        wound exudate moves towards the orifice when a negative pressure        is applied at the orifice.

According to another embodiment of the present disclosure there isprovided a method of applying TNP at a wound site, comprising:

-   -   applying negative pressure at an orifice of a cover layer of a        wound dressing comprising any of the components or features of        any wound dressing embodiment disclosed herein, a peripheral        region around the wound site being sealed with the wound        dressing such that air and wound exudate move towards the        orifice;    -   collecting wound exudate, from the wound site, through a        transmission layer of the wound dressing, in an absorbent layer        of the wound dressing; and    -   reducing the rate at which wound exudate moves towards the        orifice.

According to still another embodiment of the present disclosure there isprovided an apparatus for dressing a wound for the application oftopical negative pressure at a wound site, comprising a wound dressingcomprising any of the components or features of any wound dressingembodiment disclosed herein and/or:

-   -   an absorbent layer for absorbing wound exudate;    -   a gas impermeable cover layer overlying the absorbent layer the        cover layer comprising at least one orifice configured to allow        negative pressure to be communicated through the cover layer in        at least two spaced apart regions.

According to an additional embodiment of the present disclosure there isprovided a method of applying TNP at a wound site, comprising:

-   -   sealing a cover layer of a wound dressing comprising any of the        components or features of any wound dressing embodiment        disclosed herein around the wound site;    -   applying negative pressure at at least one orifice in the cover        layer, said at least one orifice configured to allow negative        pressure to be communicated through the cover layer in at least        two spaced apart regions; and    -   collecting wound exudate, from the wound site, in an absorbent        layer of the wound dressing.

According to another embodiment of the present disclosure there isprovided a suction port for applying negative pressure to a wounddressing of any of the embodiments disclosed herein or having any of thecomponents or features of any wound dressing embodiment disclosed hereinfor the application of topical negative pressure at a wound site, thesuction port comprising:

-   -   a connector portion for connecting the suction port to a source        of negative pressure;    -   a sealing surface for sealing the suction port to a cover layer        of a wound dressing; and    -   a liquid impermeable gas permeable filter element arranged to        prevent a liquid entering the connector portion.

According to an additional embodiment of the present disclosure there isprovided a method of communicating negative pressure to comprising awound dressing of any of the embodiments disclosed herein or having anyof the components or features of any wound dressing embodiment disclosedherein for the application of topical negative pressure at a wound site,comprising:

-   -   applying negative pressure at a connecting portion of a suction        port sealed around a perimeter of an orifice in a cover layer of        the wound dressing;    -   filtering gas drawn from within the wound dressing through a        liquid impermeable gas permeable filter element of the suction        port.

According to another embodiment of the present disclosure there isprovided a method of manufacturing a suction port for applying negativepressure to a wound dressing for the application of topical negativepressure at a wound site, the suction port having a connector portionfor connecting the suction port to a source of negative pressure and asealing surface for sealing the suction port to a cover layer of a wounddressing of any of the embodiments disclosed herein or having any of thecomponents or features of any wound dressing embodiment disclosedherein, the method comprising:

-   -   disposing a liquid impermeable gas permeable filter element of        the suction port at a location to prevent a liquid entering the        connector portion.

According to yet another embodiment of the present disclosure there isprovided an apparatus for the application of TNP therapy to a woundsite, comprising:

-   -   a first layer comprising a plurality of openings each having a        first open area;    -   a further layer spaced apart from the first layer comprising a        plurality of further openings each having a further open area;        and    -   an air impermeable, moisture vapor permeable cover layer over        the first and further layers; wherein    -   a region between the first and further layers comprises a        portion of a flow path for air and/or wound exudate flowing from        a wound site and said first open area is less than said further        open area.

According to still another embodiment of the present disclosure there isprovided a method of applying TNP therapy to a wound site, comprising:

-   -   via a vacuum pump in fluid communication with a wound dressing        of any of the embodiments disclosed herein or having any of the        components or features of any wound dressing embodiment        disclosed herein located over a wound site, applying a negative        pressure at the wound site; and    -   as liquid evaporates through a cover layer of the dressing,        preventing blockage of a fluid flowpath region of the wound        dressing.

Certain embodiments provide a wound dressing of any of the embodimentsdisclosed herein or having any of the components or features of anywound dressing embodiment disclosed herein which even when undernegative pressure conditions is able to provide further “give” to buffercompression forces from harming a wound.

Certain embodiments provide a wound dressing of any of the embodimentsdisclosed herein or having any of the components or features of anywound dressing embodiment disclosed herein able to disconnect shearforces applied to the dressing from the wound site covered by thedressing. As a result damage to the wound can be wholly or at leastpartially avoided.

Certain embodiments provide the advantage that a wound site can becovered with a wound dressing of any of the embodiments disclosed hereinor having any of the components or features of any wound dressingembodiment disclosed herein which is simultaneously able to delivernegative pressure wound therapy to a wound site, collect exudate andprovide protection from forces operating on the dressing.

Certain embodiments provide the advantage that forces operating on awound dressing of any of the embodiments disclosed herein or having anyof the components or features of any wound dressing embodiment disclosedherein can be offset by dissipating loads operating over a relativelysmall distance on an upper layer of the dressing to a relatively largerarea on a lower surface of the dressing. The force is thus dissipatedover a larger area thus reducing the effect of the force.

Certain embodiments provide the advantage that a wound dressing of anyof the embodiments disclosed herein or having any of the components orfeatures of any wound dressing embodiment disclosed herein can be usedto collect wound exudate generated during a negative pressure therapyprocess, whilst extending the useful lifetime of the dressing bytranspiring a water component of the wound exudate. A pump remote fromthe wound dressing can be connected to the wound dressing and reusedwhilst the wound dressing itself is used to collect wound exudate andmay then be disposed of after use.

Certain embodiments provide a wound dressing and/or method of applyingtopical negative pressure in which a flowpath through a wound dressingof any of the embodiments disclosed herein or having any of thecomponents or features of any wound dressing embodiment disclosed hereinis kept open so that therapy can be continued for as long as desired bya care giver.

Certain embodiments prevent solid material, which may cause a blockage,from entering a flowpath region in a wound dressing of any of theembodiments disclosed herein or having any of the components or featuresof any wound dressing embodiment disclosed herein by using a layer ofthe dressing to act as a bar to such material.

Certain embodiments prevent build-up of solid material in a flowpathregion of a wound dressing of any of the embodiments disclosed herein orhaving any of the components or features of any wound dressingembodiment disclosed herein by ensuring that any solid material thatenters into that flowpath region can always escape into a further regionof the dressing.

Certain embodiments provide the advantage that the build-up of solidmaterial in a flowpath in a wound dressing of any of the embodimentsdisclosed herein or having any of the components or features of anywound dressing embodiment disclosed herein is avoided by having anabsorbent layer close to the flowpath region store liquid over time.This helps keep the environment of the flowpath region moist which helpsavoid crusting.

Certain embodiments provide the advantage that a wound dressing of anyof the embodiments disclosed herein or having any of the components orfeatures of any wound dressing embodiment disclosed herein can be usedto collect wound exudate generated during a negative pressure therapyprocess, whilst extending the useful lifetime of the dressing bytranspiring a water component of the wound exudate. A pump remote fromthe wound dressing can be connected to the wound dressing and reusedwhilst the wound dressing itself is used to collect wound exudate andmay then be disposed of after use. Embodiments of the present disclosureare further described hereinafter with reference to the accompanyingdrawings, in which:

FIG. 1 illustrates a view through an embodiment of a wound dressing ofthe present disclosure;

FIG. 2A illustrates a plan view of the dressing of FIG. 1;

FIG. 2B illustrates a perspective view of the dressing of FIG. 1;

FIGS. 3A-3C illustrate 2 known dressings (3A and 3B) and an embodimentof a dressing of the present disclosure (3C);

FIG. 4 illustrates a graph of odour capture ability of various wounddressings;

FIG. 5 shows photographs of a prior art dressing and an embodiment of adressing of the present disclosure;

FIG. 6 shows photographs of a prior art dressing and an embodiment of adressing of the present disclosure over time;

FIG. 7 shows a photograph of an embodiment of a dressing of the presentdisclosure applied to a patient;

FIG. 8 illustrates a graph of the results of tests monitoring lifting ofdressings over time;

FIG. 9 illustrates a graph of the percentage of compression of variousdressings after a known force was applied to each dressing;

FIG. 10 illustrates the contact area where force is applied after apoint pressure is applied to various dressings;

FIGS. 11A and 11B illustrate various obscuring elements;

FIG. 12A illustrates an alternative dressing arrangement;

FIG. 12B illustrates another dressing arrangement;

FIG. 12C shows a photograph of yet a further dressing arrangement;

FIG. 13 illustrates a graph of pressure transfer through variousdressings; and

FIG. 14 illustrates UV-visible spectrum absorbency of various materials.

FIG. 15A illustrates an embodiment of a wound dressing;

FIG. 15B illustrates another embodiment of a wound dressing;

FIG. 16 illustrates a top view of an embodiment of a wound dressing;

FIG. 17 illustrates a top view of an embodiment of a wound dressingembodiment, which can be any dressing embodiment disclosed herein,including baffle elements;

FIG. 18 illustrates a top view of a further wound dressing embodiment,which can be any dressing embodiment disclosed herein, including baffleelements;

FIG. 19 illustrates a baffle element according to one embodiment;

FIG. 20 illustrates a top view of an embodiment of a wound dressing,which can be any dressing embodiment disclosed herein, including asingle baffle element;

FIG. 21 illustrates a top view of an embodiment of a wound dressing,which can be any dressing embodiment disclosed herein, including an airchannel;

FIG. 22 illustrates a top view of an embodiment of a wound dressing,which can be any dressing embodiment disclosed herein, including two airchannels;

FIG. 23 illustrates a top view of an embodiment of a wound dressing,which can be any dressing embodiment disclosed herein, including twoorifices in a cover layer coupled through a fluid communication passage;

FIG. 24 illustrates an embodiment of the fluid communication passage;

FIG. 25 illustrates a top view of a suction port;

FIG. 26 illustrates a suction port including a filter element;

FIG. 27 illustrates a further suction port including a filter element;

FIGS. 28A-L illustrate a range of exemplifying configurations of baffleelements in a wound dressing, which can be any dressing embodimentdisclosed herein;

FIG. 29 illustrates an exemplifying configuration of vias in atransmission layer of a wound dressing, which can be any dressingembodiment disclosed herein;

FIG. 30 illustrates a top view of a wound dressing, which can be anydressing embodiment disclosed herein, including an elongate orifice in acover layer;

FIG. 31 illustrates a transmission layer in a relaxed mode of operation;

FIG. 32 illustrates a transmission layer in a forced mode of operation;

FIG. 33 illustrates pressure offsetting;

FIG. 34 illustrates a transmission layer and overlying absorbent layerin a relaxed mode of operation;

FIG. 35 illustrates an absorbent layer and transmission layerexperiencing a compressive force;

FIG. 36 illustrates an absorbent layer and transmission layerexperiencing a shear force;

FIG. 37 illustrates a cross-section of a region of an embodiment of awound dressing;

FIG. 38 illustrates a lower layer of a transmission layer used in anembodiment of a wound dressing, which can be any dressing embodimentdisclosed herein;

FIG. 39 illustrates an upper layer of a transmission layer used in anembodiment of a wound dressing, which can be any dressing embodimentdisclosed herein;

FIG. 40 illustrates a lower surface of a transmission layer used inanother embodiment of a wound dressing, which can be any dressingembodiment disclosed herein;

FIG. 41 illustrates an upper surface of a transmission layer used inanother embodiment of a wound dressing, which can be any dressingembodiment disclosed herein;

FIG. 42 illustrates an embodiment of a wound treatment system; and,

FIGS. 43A-D illustrate the use and application of an embodiment of awound treatment system onto a patient which can be used with anydressing embodiment disclosed herein.

In the drawings like reference numerals refer to like parts.

Throughout this specification reference is made to a wound. It is to beunderstood that the term wound is to be broadly construed andencompasses open and closed wounds in which skin is torn, cut orpunctured or where trauma causes a contusion. A wound is thus broadlydefined as any damaged region of tissue where fluid may or may not beproduced. Examples of such wounds include, but are not limited to,incisions, lacerations, abrasions, contusions, burns, diabetic ulcers,pressure ulcers, stoma, surgical wounds, trauma and venous ulcers or thelike. The wound dressing may be used for a human or other living being.

In some embodiments, it may be preferable for the wound site to befilled partially or completely with a wound packing material. This woundpacking material is optional, but may be desirable in certain wounds,for example deeper wounds. The wound packing material can be used inaddition to the wound dressing. The wound packing material generally maycomprise a porous and conformable material, for example foam (includingreticulated foams), gauze or a hydrofibre ribbon. Preferably, the woundpacking material is sized or shaped to fit within the wound site so asto fill any empty spaces. The wound dressing may then be placed over thewound site and wound packing material overlying the wound site. As usedherein the term ‘exudate’ is used to broadly cover any of wound exudate(such as cells, infection by products, cellular debris, proteins, etc.),blood or any other matter released from a wound.

As an overview, the present disclosure relates to an absorbent dressing,where the particular layers provide individual properties to thedressing, and where the combination of these layers in a particularorder provides additional properties.

Below are described several properties of such a multi-layered dressing,which can be incorporated independently or in combination with eachother.

(a) Dressing pad assembly with layers arranged so that odour control isplaced between two layers of different rates of absorptions. This forcesthe fluid through the odour control layer, but ensures it does notremain saturated with fluid, which enables it to remain efficient.

Odour control can also be achieved by incorporating odour-controlmaterials within some of the other layers of the pad.

Differential absorption also helps to limit the risk of maceration closeto the skin, as the foam layer (closest to the wound) is drained of itsexcess fluid by the superabsorber layer (on the other side of the odourcontrol layer). The superabsorber layer does not allow fluid to bereleased in liquid form under compression, and fluid can only leave thislayer by evaporation, or wicking transfer to a further layer. Thesuperabsorber layer can be shaped to a larger size than the lowest padlayer, to ensure adequate protection against potential leaks byproviding a highly absorbent zone at the very edge of the pad. This canalso be achieved by including a ring of highly absorbent materialsuperimposed on the pad assembly.

(b) Dressing containing a means of partially obscuring the top surface.The effect is to reduce the visibility of unsightly exudates whileallowing clinical judgment on the state of the dressing. This iscurrently achieved by using a visual masking layer, where overlappingfabrics with openings are disposed slightly offset of each other, forexample. While this method allows fluid to wick up through this layerand reach the top film, coloured solids remain onto the layer below,thus containing the coloured solid matter at a little distance from thetop film and providing a reduced aesthetics impact.

(c) A dressing design that has enhanced compatibility with body movementby means of:

-   -   Using pad components which can deform plastically under the        pressures used to apply dressings (unlike purely foam dressings        which tend to apply tension forces to resume their initial flat        shape) and retain the shape they have been given around a part        of the body    -   Having no, or minimal, means of bonding the layers together, to        ensure that the dressing composition does not offer resistance        to movement by providing resistance to internal shear    -   A larger border to increase article retention, and the area of        elastic stretch that can follow the movement of the skin    -   Shaping the dressing such that sub-areas of the pad can move        independently from each other without compromising the overall        position or integrity of the dressing    -   Using different dimensions of the pad components to minimise the        angle of incidence of the dressing edge, which links to reduced        resistance to rubbing onto textile

These can be used individually or in combination of any number, howeverthe effect is maximised by using all options in one embodiment.

(d) A dressing pad design that provides enhanced protection againstmechanical forces, both from the outside (shocks, knocks, shear) and theinside (pressure onto wounds from bony protrusions).

Protection against the ill effects of direct pressure can be achieved byincorporating, in the structure of the dressing, a means of spreading apoint pressure into a proportionally lower pressure across a largersurface area.

In particular, the use of three-dimensional knits, such as spacerfabrics, can provide the desired effect. The vertical filaments bondingtwo horizontal knitted layers can help to initially resist collapse ofthe dressing structure, and spreading of the pressure across a widerarea than that of the point force applied. The yield point at which thedressing collapses completely can therefore be seen at higher forcesthan what traditional foam dressings can withstand.

Pressure distribution maps can also show that such a 3-D structure canspread a point force to a wider area than a foam layer of the samethickness can.

Protection against shear can be achieved by ensuring that the componentsof the dressing can themselves shear compared to each other: this candiminish what shear forces are being transmitted through to the skin orthe wound.

(e) A dressing pad assembly where the following properties are beingprovided by given material layers, and where the respective position ofthese layers provides additional properties on top of those from theindividual layers. The description below describes the pad compositionfrom the side closest to the wound (i) to the side furthest from thewound (v):

i. Initial fluid uptake into the dressing pad, through a wound contactlayer, via a soft, hydrophilic polyurethane foam layer (reduced risk ofmaceration, comfort, maintain moist wound healing environment)

ii. Odour-control of the fluid taken up via a layer of activatedcharcoal cloth, which performs in a wet state (odour control)

iii. Transfer of fluid through this odour-control layer and onto anabsorbent layer, which does not release the fluid back out in liquidform (reduced risk of maceration, maintain moist wound healingenvironment)

iv. Impact and shear protection through a three-dimensional knittedfabric, which offers resistance to pressure transfer onto the wound(shock and knock protection)

v. Partial masking of the uppermost surface of the pad through asemi-opaque component (enhanced aesthetic appearance during wear,allowing clinical judgement)

Combination of (ii) and (iii) enhances the odour control capability, asthis helps to reduce the fluid saturation of the odour control layer andmaximise its efficacy.

Combination of (iii), (iv) and (v) to ensure that fluid is beingevaporated from the superabsorber layer, out of the dressing through themoisture-vapour permeable top film.

For all the dressing pads described (a) to (e), the pad is containedbetween a wound contact layer and a top film.

The wound contact layer can comprise a perforated wound-side adhesivewhich can be a silicone adhesive, or a low-tack adhesive to minimiseskin trauma on removal. The wound contact layer comprises a supportmaterial which can be a mesh, a net or a perforated film. It can alsocomprise a construction adhesive on the pad side, to ensure its intimatecontact with the lowest part of the pad, and therefore efficient uptakeof fluid from the wound without pooling.

The top film is a liquid-impermeable, moisture-vapour permeable,breathable film, which allows moisture to evaporate from the dressing.

FIGS. 1, 2 a and 2 b respectively show a schematic cross-sectional view,a plan view and a perspective view of a wound dressing according to anembodiment of the present disclosure. The wound dressing 100 includes anumber of layers that are built up in a generally laminar fashion toform a dressing having a relatively planar form. The wound dressing 100includes a border region 110 extending around the outer periphery of thedressing and a raised central region 112 in the centre of the dressing(in plan view). The precise dimensions of the border region and thecentral region may be predetermined to suit a particular wound orparticular wound type. There may be no border region required. Here theborder region has the general function of providing an area forsealingly engaging with a patient's skin surrounding a wound site toform a sealed cavity over the wound site. The central region is thelocation of further functional elements of the wound dressing.

The dressing 100 includes a perforated wound contact layer (101) and atop film (102).

Further components of the wound dressing 100 include:

-   -   A layer of polyurethane hydrocellular foam (103) of a suitable        size to cover the recommended dimension of wounds corresponding        to the particular dressing size chosen    -   A layer of activated charcoal cloth (104) of similar or slightly        smaller dimensions than (103), to allow for odour control with        limited aesthetic impact on the wound side.    -   A layer of superabsorbent air-laid material (105) containing        cellulose fibres and a superabsorbent polyacrylate particulates,        of dimensions slightly larger than (103) to allow for an overlap        of superabsorbent material acting as leak prevention    -   A layer of three-dimensional knitted spacer fabric (106),        providing protection from pressure, while allowing partial        masking of the top surface of the superabsorber, where coloured        exudate would remain. In this embodiment this is of smaller        dimension (in plan view) than the layer (105), to allow for        visibility of the edge of the absorbent layer, which can be used        by clinicians to assess whether the dressing needs to be        changed.

In this embodiment the wound contact layer 101 is a perforatedpolyurethane film that is coated with a skin-compatible adhesive, suchas pressure sensitive acrylic adhesive or silicone adhesive (not shown).Alternatively the wound contact layer may be formed from any suitablepolymer, e.g. silicone, ethylvinyl acetate, polyethylene, polypropylene,or polyester, or a combination thereof. The skin-compatible adhesive iscoated on the lower side of the layer 101, i.e. the side that is tocontact the patient. Aptly the adhesive is coated as a continuous layeron the underside of the layer 101. Optionally the adhesive may be coatedin a semi-continuous layer such as in a pattern such as a chequerboardpattern, polka dot pattern, herring bone pattern, mesh pattern or othersuitable pattern. Alternatively the adhesive may be coated around aborder region 110 of the dressing only, and not in a central region 112of the dressing (as viewed from above in plan view) such that theadhesive may adhere to skin surrounding a wound and not the wounditself. The perforations allow the wound contact layer to be permeableto liquid and gas. The perforations are through holes extending from anupper surface to a lower surface of the wound contact layer to enablefluid to flow through the layer. The perforations are small enough tohelp prevent tissue ingrowth into the wound dressing yet still allowfluid to flow. The perforations may be slits or holes having a sizerange of 0.025 mm to 1.2 mm for example. The upper surface of layer 101may optionally be coated with adhesive, to help in the construction ofthe dressing. Aptly the adhesive may be a pressure sensitive adhesiveand aptly the same adhesive as used on the lower surface of the layer101.

The absorbent layer 103 of polyurethane hydrocellular foam is locatedover the wound contact layer 101 and extends over the central region 112of the wound contact layer.

The term hydrocellular is a term given to foams that are absorbent,hydrophilic and polymeric. The foams may have a particular range of cellsize of 30 microns to 700 microns.

The foam is in this case of polyurethane, hydrophilic, conformable,resilient, and porous and allows fluids such as wound exudate to bedrawn away from the wound site and further into the dressing. However,the foam also maintains a sufficiently moist wound healing environmentso as to not dry out the wound, retaining a balanced moist atmosphereunder the dressing. An optimal wound healing environment generallyrequires the area of the wound to have some level of moisture yetwithout excessive fluid.

The absorbent employed in the absorbent layer of the dressings may beany suitable polymer foam. The foam is aptly a highly conformablehydrophilic foam, aptly an open celled foam, and more aptly the foam isa mixture of open and closed cells.

The absorbent layer used in dressings of the present disclosure iscapable of absorbing wound exudate. It is desirable that the foam layerabsorbs the wound exudate rapidly. Such rapid absorption preventsundesirable pooling of exudate between the dressing and the wound.

The ability of polymer foam layers to absorb and retain fluids dependsto some extent on the size of the foam cells, the porosity of the foamand the thickness of the foam layer.

Suitable open cell foams of dressing embodiments of the presentdisclosure have a cell size of 30 microns to 700 microns and aptly acell size of 50 microns to 500 microns. Apt open cell hydrophilic foamsof dressings of the present disclosure have 20% to 70% and preferably30% to 60% of the total membrane area of the cells as membrane openings.Such open cell foams permit transport of fluid and cellular debris intoand within the foam. Apt foams may be polyurethane, carboxylatedbutadiene styrene rubber, polyacrylate or the like foam. Such foams maybe made of hydrophilic materials per se or may be treated to render themhydrophilic, for example with surfactants. It is preferred to use foamsthat are made of polymer that is itself hydrophilic as it has been foundthe exudate is less likely to coagulate rapidly. Favoured hydrophilicpolymer foams are hydrophilic polyurethane and especially those whichare made of crosslinked hydrophilic polyurethane. Preferred foams can bemade by reacting a hydrophilic isocyanate terminated polyetherprepolymer with water. Suitable hydrophilic polyurethane foams of thistype include those known as Hypol™ foams. Hypol™ foams can be made fromHypol hydrophilic prepolymers marketed by W. R. Grace and Co and arehydrophilic cellular foams having a mixture of open and closed cells.Hypol™ based foams are also available from Dow Chemicals. Other suitablefoams are described in WO91/01706 in relation to the absorbent layerdescribed, incorporated herein by reference, and in WO93/04101 alsoincorporated herein by reference.

The use of such foams of hydrophilic polymer in the absorbent pad ofdressings of the present disclosure can allow the wound to be maintainedin a moist condition even when the exudate produced has been absorbedand removed from the wound surface.

A further function of the foam layer is to wick away excess fluid fromthe wound area via its open cells. It is noted that PU foam itself canabsorb liquid, the whole polymer swelling.

The odour-removing layer of activated charcoal cloth 104 is providedover the layer of foam 103. In this embodiment the activated charcoallayer is about the same length and depth as the foam layer and thereforelies over the foam layer to cover about the same area. The layer may beof Zorflex® cloth available from Chemviron Carbon, for example.Alternative suitable materials are manufactured by MAST under the tradename C-TeX®.

The function of the odour-removing layer is to help prevent or reduceodour originating from the wound from transmitting out of the dressing.

It is noted that in this example the odour-removing layer is provided asa loose layer, unbonded to the adjacent layers, though alternatively thelayers may be bonded by adhesive or stitching, etc.

The layer of absorbent material 105 is provided over the odour-removinglayer 104. The absorbent layer 105 extends fully over the layer 104, aswell as over the side portions of both the odour-removing layer 104 andfoam layer 103. The absorbent material may be a foam, woven or non-wovenor knitted natural or synthetic material and may optionally include orbe super-absorbent material. A suitable material may be an air-laidmaterial containing cellulose fibres and superabsorbent polyacrylateparticulates or fibres, for example superabsorber cores available fromNovathin. Alternatively the absorbent layer 105 may be manufactured fromALLEVYN™ foam, Freudenberg 114-224-4, Chem-Posite™11C-450, CMC (e.g.Medline Maxsorb with Alginate), alginate (e.g. ActivHeal Alginate byAdvanced Medical Solutions) and/or polyacrylate fibres (e.g. SAF™ byTechnical Absorbent Ltd).

The layer 105 forms a reservoir for fluid, particularly liquid, removedfrom the wound site and draws those fluids towards a cover layer 102.The material of the absorbent layer also prevents liquid collected inthe wound dressing from flowing freely once in the dressing structure.The absorbent layer 105 also helps distribute fluid throughout the layervia a wicking action so that fluid is drawn from the wound site andstored throughout the absorbent layer, i.e. transferring and locking inthe liquid. This prevents agglomeration in areas of the absorbent layer.The capacity of the absorbent material should be sufficient to managethe exudate flow rate of a wound for the predetermined life of thedressing, whether the wound is acute or chronic. Again, in combinationwith the foam layer, the layer 105 aptly should not cause the wound tobecome completely dry. This might occur if, for example, thesuperabsorbent material were to dry out the foam layer and thensubsequently the wound area.

Aptly, the absorbent layer is a layer of non-woven cellulose fibreshaving super-absorbent material in the form of dry particles dispersedthroughout. Use of the cellulose fibres introduces fast wicking elementswhich help quickly and evenly distribute liquid taken up by thedressing. The juxtaposition of multiple strand-like fibres leads tostrong capillary action in the fibrous pad which helps distributeliquid. In this way, the super-absorbent material is efficientlysupplied with liquid. Also, all regions of the absorbent layer areprovided with liquid.

The absorbent layer 105 aptly has a high osmotic potential so as toprevent liquid being released from the layer, even when the layer isunder compression (e.g. if the dressing area is pressed or leant on).Liquid may however leave the layer by diffusion through evaporation orpossibly wicking transfer to a further layer.

The layer of absorbent material 105 may be of any suitable dimensions.Aptly, if the layer is shaped to a size larger than the layers betweenitself and the wound contact layer, then the layer can fold over theedges of any intermediate layers, acting as an enclosure such that anyfluid moving into the dressing will encounter the absorbent layer priorto encountering the top film or the adhesive wound contact layer. Thishelps to prevent possible leaks of fluid from the dressing. As analternative, a ring shaped (annular or torus) or other suitable bordershaped portion of absorbent material may be added to a dressingseparately from the absorbent layer to surround underlying layers and toperform the same function as the overlying edge of the absorbent layer.

Optionally, according to certain embodiments of the present disclosure,the absorbent layer may include synthetic staple fibres and/orbi-component staple fibres and/or natural staple fibres and/orsuper-absorbent fibres. Fibres in the absorbent layer may be securedtogether by latex bonding or thermal bonding or hydrogen bonding or acombination of any bonding technique or other securing mechanism. Aptly,the absorbent layer is formed by fibres which operate to locksuper-absorbent particles within the absorbent layer. This helps ensurethat super-absorbent particles do not move external to the absorbentlayer and towards an underlying wound bed.

Aptly, the fibres are strand-like and made from cellulose, polyester,viscose or the like. Aptly, dry absorbent particles are distributedthroughout the absorbent layer ready for use. Aptly, the absorbent layercomprises a pad of cellulose fibres and a plurality of super absorbentparticles. Aptly, the absorbent layer is a non-woven layer of randomlyorientated cellulose fibres.

Super-absorber particles/fibres may be, for example, sodium polyacrylateor carbomethoxycellulose materials or the like or any material capableof absorbing many times its own weight in liquid. Aptly, the materialcan absorb more than five times its own weight of 0.9% W/W saline, etc.Aptly, the material can absorb more than 15 times its own weight of 0.9%W/W saline, etc. Aptly, the material is capable of absorbing more than20 times its own weight of 0.9% W/W saline, etc. Aptly, the material iscapable of absorbing more than 30 times its own weight of 0.9% W/Wsaline, etc.

Aptly, the particles of superabsorber are very hydrophilic and grab thefluid as it enters the layer, swelling up on contact. An equilibrium isset up within the dressing core whereby moisture passes from thesuperabsorber to the top film and the fluid vapour starts to betranspired. A moisture gradient may be established within the dressingto continually remove fluid from the wound bed.

The shielding layer 106 is a layer having a 3-dimensional structure thatmay include open cell foam (e.g. Alleyvn™ foam by Smith & Nephew,Biatain foam by Coloplast or Advanced Medical Devices' ActivHeal foam),a knitted or woven spacer fabric (for example Baltex 7970 weft knittedpolyester or Baltex XD spacer fabric or Surgical Mesh's Polyester feltor Polyester mesh) or a non-woven fabric (e.g. Fiberweb's S-tex orSecuron). Alternatively the shielding layer may be a completely opaquepolymer film having cut-out windows or perforations, for example (e.g.SNEF's H514 or H518 blue net). Here the layer 106 is of polyester thatincludes a top layer (that is, a layer distal from the wound in use),which is a 84/144 textured polyester, a bottom layer (that is, a layerthat lies proximate to the wound in use), which is a 100 denier flatpolyester and a third layer formed sandwiched between these two layers,which is a region defined by a knitted polyester viscose, cellulose orthe like monofilament fibre. Of course other materials and other linearmass densities of fibre could be used, including for example amultistrand alternative. The shielding layer 106 may be similar oridentical to the materials described in US2011/0282309 in relation tothe transmission layer (FIGS. 23 to 27).

The layer 106 allows the transmission therethrough of any gas or vapourto the top film 102 and may therefore be considered as a transmissionlayer.

Aptly the layer 106 performs one or more further functions includingacting as a partial masking layer and acting as a force distributing(impact protection) layer.

Partial masking of wound exudate, blood or other matter released from awound may be achieved with overlapping perforated fabrics disposedsomewhat offset from each other, such as shown in FIG. 11(b). As shownin (b), a shielding layer is itself formed from 3 sub-layers, such asthe 3-D knit material described above. The perforated top and bottomlayers allow transport of vapour and gas, and are offset from gaspathways in the central knitted layer. As such, vapour and gas maytravel through the layer, but the coloured exudate cannot be seen, ortravel, through the layer.

Alternatively, as shown in FIG. 11(a), a perforated cover layer 1102 isprovided over a perforated shielding layer 1106, which allows moisturevapour and gas to be transmitted away from the dressing, yet providessufficient masking for exudates to be visible only to a trainedclinician.

More specifically, it is known that when a film is breathable (able totransmit vapour), then it is likely to allow colour to transmittherethrough. Even if a breathable film includes a coloured pigment formasking a lower layer, when exudate fluid contacts the film, colouredelements in the exudate can be carried into contact with the film andchange the colour perception from the film, and be visible to the user.This allows fluid to transmit through the layer towards the top filmwhilst coloured solids or liquids remain bound in the absorbent layerbelow. Exudate colour is principally due to proteins and biologicalbreak down products from tissue or blood cells, which tend to be largemolecules.

Another function of the shielding layer 106 may be for pressuredistribution and impact protection. For example, if the patientaccidentally knocks the wound area, leans on the wound area or anothercause applies a pressure to the dressing covering a wound. Aptly theshielding layer is provided closer to where the pressure is beingapplied than other layers of the dressing.

The shielding layer 106 acts as a pressure spreading component,receiving a pressure on one side thereof (possibly a point force) andspreading the pressure over a wider area, thus reducing the relativepressure received on the other side of the shielding layer. As such, thelevel of pressure felt by the patient at the wound site is reduced.

A form of shielding layer that has been found to be a good pressuredistributed is a layer having non-ordered fibres or strands, i.e. fibreslying at different angles with respect to each other, for example theknitted spacer fabric of Baltex 7970.

The absorbent layer 105 may also act as a pressure spreading component.A combination of the shielding layer 106 and the absorbent layer 105 hasbeen found to give particularly apt pressure distributing properties.However, only one pressure spreading component may be sufficient.

In general, a material that is relatively non-deformable is moresuitable for spreading point pressure. However this should be balancedby the requirement for deformation ability for the dressing to adhere toa non-planar body part.

When a pressure occurs from inside the patient's body, such as pressurefrom a protruding bone, the shielding layer may be somewhat lessefficient at spreading the pressure if it is positioned towards thedistal part of the dressing. However, any equal and opposite reaction offorce acting back toward the patient's skin will be spread by theshielding layer 106 and absorbent layer 105 (e.g. if the patient islaying on something hard such as the ground or hard chair). The pressurespreading response will depend somewhat upon the hardness of the surfaceagainst which the patient and dressing are pressed against, if any.

The pressure spreading ability of these layers may also be usefulagainst slower, constant pressures as well as rapid point forces.

The top film 102 is a cover layer for covering the lower layers of thedressing, helping to encapsulate the layers between the wound contactlayer and the top film. The top film 102 is in this case a layer ofpolyurethane, Elastollan (trade name) SP9109 manufactured by BASF. Thetop film may be coated with any suitable adhesive. Aptly the adhesivewill be a pressure sensitive adhesive e.g. acrylic adhesive or siliconeadhesive.

As such, the top film 102 helps to ensure that the dressing remainsbreathable, i.e. allows a proportion of fluid absorbed in the dressingto be evaporated via the outer surface of the dressing. In this waycertain fluid content of the exudate can be transpired from thedressing, reducing the volume of remaining exudate and increasing thetime before the dressing becomes full. Also, the wound contact layer 101and top cover 102 help to ensure that the border region 110 of thedressing remains breathable, i.e. allows a patient's normal skinperspiration to be evaporated through the dressing, which helps inpreventing or minimising skin maceration.

The outer layer of dressings of the present disclosure when present canbe a continuous conformable film. The continuous moisture vapourtransmitting conformable film outer layer of the wound dressing may beused to regulate the moisture loss from the wound area under thedressing and also to act as a barrier to bacteria so that bacteria onthe outside surface of the dressing cannot penetrate to the wound area.Suitable continuous conformable films will have a moisture vapourtransmission rate of at least 300, aptly from 300 to 5000 gramspreferably 500 to 2000 grams/square meter/24 hrs at 37.5 C at 100% to10% relative humidity difference. Such moisture vapour transmission rateof the continuous film allows the wound under the dressing to heal undermoist conditions without causing the skin surrounding the wound tomacerate. To ensure the use of an adhesive on the top film 102 does notreduce the moisture vapour transmission rate, a hydrophilic waterdispersible adhesive may be used e.g. hydrophilic acrylic adhesives.Although, other suitable adhesive may also be used. Aptly adhesive mayalso be spread across the surface of the film in the form of a patternsuch that a portion of the area of the film does not contain adhesive.E.g., use of a polka dot pattern whereby adhesive is not present in thedot area and 5 to 95%, or aptly 10 to 80%, more aptly 30 to 70%, moreaptly 40 to 70%, more aptly 40 to 60%, more aptly 40 to 50% of the areaof film does not contain adhesive. It will be apparent to those skilledin the art that any suitable pattern of adhesive layer may be used toproduce a top film 102 that is not fully coated with adhesive and thusmaximises the moisture vapour transmission rate. Other suitablematerials for the cover layer are described in WO91/01706 in relation tothe conformable moisture vapour transmitting outer layer.

Additionally, the top film may act as a further barrier to any remainingodour from being transmitted out of the wound dressing, since the topfilm may include through holes that allow molecules of a predeterminedmaximum size to pass therethrough.

FIGS. 2a and 2b show a possible shape of a dressing, useful for enhancedcompatibility with body movement, where each layer is shaped to reducethe incident angle of the pad edge, and to provide somewhatindependently moving sub-sections of the dressing. The dressing border,including the wound contact layer (101) and the top film (102) can alsocomprise slits, provided to further enhance the conformability onapplication by allowing the borders to overlap if needed.

Reverting back to FIG. 1, it can be seen that the cross-section of thedressing includes various layers stacked in a contiguous manner so as toform a generally laminate structure. Preferably the dressing is moisturevapour permeable. The layers shown in FIG. 1 are of different widths anddimensions, though other arrangements are also possible.

In the border region 110, the top film 102 abuts with the wound contactlayer 101. A moisture vapour transmitting adhesive layer is provided(not shown) in the border region 110 between the layers 101, 102 to bondthe layers in that region. Suitable adhesives that are moisture vapourtransmitting include various acrylate ester copolymer and polyvinylether pressure sensitive adhesives for example as described in UK patentnumber 1280631. Aptly the adhesives may be copolymers of an acrylateester with acrylic acid for example as described in UK patentapplication number 2070631.

The dimensions of the components are arranged so as to minimise theangle of incidence of the dressing edge. This helps to reduce rubbing ofthe dressing against textiles and reduced snagging of the dressingagainst textile, by reducing the change in profile of the dressingthroughout the thickness of the dressing.

In use, a wound dressing as described above would be applied to a woundsite of a patient with the surface of the wound contact layer 101 facingthe wound site. Any wound exudate, blood or other wound fluid wouldtravel into the dressing via the wound contact layer and sequentiallayers above the wound contact layer. Fluid would permeate through thefoam layer, the activated charcoal layer, and then reach the absorberlayer at which point preferably the liquid would not go any further andbe retained by the absorber layer. On the other hand, gas and moisturevapour would be able to permeate further via the shielding layer and/ortop film.

FIG. 3 shows the difference between the appearance of existing dressingsand of a dressing of the present disclosure after use on a wound model.The photographs (a) and (b) are known dressings. The photograph (c) is awound dressing according to the present disclosure. The regionidentified by reference number 114 is the area of the central region 112that is not covered by the shielding layer 106. As such, the absorbentlayer 105 is directly adjacent the top film 102 in this area. Since theshielding layer 106 acts as a partial masking layer, the region 114 maybe used by a clinician or other trained user to assess the spread ofwound exudate throughout the dressing. This assessment will be helped bythe dressing being placed approximately central over a wound such thatexudate reaches the radially outer region 114 after the exudate hasreached the more central areas (e.g. that covered by the shielding layer106). Aptly, the clinician may be trained to assess the spread of woundexudate using the region 114 as a guide, for example with instructionsthat less than 50% coverage of the region 114 with exudate does notrequire changing of the dressing, about 50% coverage of the region 114indicating the time to consider changing the dressing, and more than 50%coverage of the region 114 with exudate does require changing of thedressing. Of course the area of the central region 112 covered with theshielding layer 106, which acts as a partial masking layer, may also oralternatively be used to assess the spread of exudate by a trainedclinician. In addition, the dressing may have various other instructionsfor use, for example including a recommended maximum duration that thedressing may be used, e.g. 7 days, regardless of the assessment of thespread of exudate.

FIG. 4 shows the odour control performance of the present disclosure(Design A) when wet, compared to existing dressings. This was measuredby incubating dressing samples with solutions of odorous compounds invials, for 24 h at 37° C. The headspace of the vials was subsequentlymeasured by gas-chromatography headspace, for the concentration ofodorous compounds remaining in the headspace. The efficiency in odourreduction was measured as a percentage remaining compound, compared to apositive control of incubated odorous compound only. Performance acrossfour different compounds was collated in a single measure, representedin FIG. 4. It can be seen that a dressing according to the presentdisclosure (with the arrangement of FIG. 1) performs very well inremoving odour, with less than 5% odour remaining in the headspace. Bycomparison, foam dressings perform relatively poorer with higher amountsof odour remaining.

FIG. 5 shows the comparative performance of different shapes ofdressings when placed on a tube. It can be seen that a dressingaccording to the disclosure (with the arrangement of FIG. 1), as shownon the right hand side, remains adhered to the tube after 2.5 hours,whilst a conventional dressing as shown in the left hand side lifts awayfrom the tube after the same 2.5 hours.

The wound dressing of the disclosure may be of any suitable shape orform or size. The overall dimensions of the dressing may be, forexample, 160 mm diameter, although any total size may be used, and thesize may be determined to match particular wound sizes.

In addition, it is noted that the dressing's improved conformabilitywith non-planar (bodily) shapes can be achieved in part by combining afoam with a material that could be only returned to its initial shape bya force higher than that applied onto it by foam. The role of thissecond material is to remain in the shape it was given at theapplication of the dressing, despite the forces applied to it by thefoam material trying to relax after deformation at application. E.g.airlaid or non woven material with broken or displaced fibres by theinitial application force could provide sufficient resistance againstpressure of a hydrocellular foam layer (2 to 4 mm).

The inventors have realised that a dressing formed from foam only willtend to revert to its natural position (planar or flat in the case ofthe foam layers described here). The foam has a ‘memory’ of how it wascut and manufactured. Thus when foam dressings are applied with adhesiveonto non-flat body parts the adhesive must be sufficiently strong tooppose the force of the foam reverting to its original shape.

As shown in FIG. 6, the performance of a dressing in terms of retentionof formed shape including a foam layer and a deformable layer, e.g. alayer similar to the absorbent layer 105 (Sample 6b), has been shown tobe much improved compared to a dressing that is formed from a foam only(Sample 6a).

That is, sample 6a included a wound contact layer having an adhesive onits ‘wound facing’ side, a foam layer (such as layer 103) and a coverlayer (such as top film 102). Sample 6b included a wound contact layerhaving an adhesive on its ‘wound facing’ side, a foam layer (such aslayer 103), an absorbent layer (such as layer 105), a shielding layer(such as layer 106) and a cover layer (such as top film 102).

The initial shapes of the two samples shown in FIG. 6 are planar. Uponcompressing the samples into a tightly deformed shape (as shown at time0), the shape of the samples was monitored over time to view anyreactive movement by the sample overcoming the force of the adhesive onthe wound contact side. After 5 minutes the Sample 6a had returned toits initial planar shape. Sample 6b reverted somewhat back towards itsinitial shape after 5 minutes, approximately 50% between its initialdeformation shape and the planar form. After 24 hours Sample 6b remainednon-planar.

It is believed that components of the dressing of the disclosure, suchas the absorbent layer or shielding layer, can plastically deformwithout memory, by components within the layers being displaced orbroken to some degree. For example, some of the fibres in the shieldinglayer may be broken (without overall damage to the dressing). Thisdisplacement or breakage is long term or permanent. As such the force ofthe foam layer of the dressing reverting to its original shape iscounteracted by the displaced or broken components within other layers.As such, as long as the force of the foam layer is lower than the forceof returning the other layers to a planar position, the dressing willretain its formed (non-planar) shape.

FIG. 7 shows an example of a dressing applied to a human patient, withsub-areas 701 _(a-d) applied at different angles relative to each other,and that can move independently of each other. As shown the dressing hasbeen applied to the base of the neck and shoulder region of a patient.This region requires the lobes or subareas to be applied at differentangles to each other. It is noted that there is no specific dividingline (such as perforation or other fold line) between the sub areashere.

It can be seen that not only the conformability of the materials of thedressing, but also the discrete sub-areas of the dressing help to keepthe dressing adhered to the uneven surface of the patient.

FIG. 8 illustrates the testing of a wound dressing having sub areascompared to a comparative known dressing with square profile. The liftof the dressing, i.e. movement returning back to the original flat,planar shape, was monitored over 7 days on 25 healthy volunteers. Thatis, 25 volunteers wore one wound dressing according to the disclosureand one rectangular dressing. The dressings were applied to the thighsof each volunteer. For each volunteer, after 1, 3 and 7 days of wearingthe dressing, the presence of any lifting of dressing border that haddetached away from the skin of the volunteer was determined. The graphindicates the percentage of the number of dressings in total that showedany lifting.

As shown in FIG. 8, it can be seen that the dressing having a shape withfour lobes or subareas (as per FIGS. 2a and 2b ) performed better thanthe square shaped dressing. The percentage of the dressings with subareas that showed any sign of lifting away from the volunteer's skin wason average just over 50% of the dressings after 7 days wear. For thesquare dressing, the percentage of the dressings showing signed oflifting away from the volunteer's skin was on average 70% of the totalafter 7 days wear.

The dressing shape has a rotational symmetry about its centre point (inplan view). In this example the dressing has 4 lobes. The shape of thecentral region 112 matches the shape of the border region 110 such thatthe width of the border region is approximately equal around the entiredressing. Aptly the border may be between about 12.5 mm and about 29 mm.More aptly the border is about 25 mm. Of course the border size willdepend on the full dimensions of the dressing. Other numbers of lobesmay be used such as 3, 5, 6, 7, 8, etc. The isotropic nature of thedressing shape gives the advantage that the user is not required toorientate the dressing in a specific manner before applying the dressingto a wound. The shape also enables the dressing to be adaptable tovarious parts of the body.

The dressing shape with 4 sub areas (lobes) aptly gives a maximum padarea with respect to the border area, yet has increased flexibilitycompared to a square dressing.

The inventors also performed tests upon various dressings with respectto the dissipation of force applied to the dressing. FIG. 9 illustratesthe degree of (percentage of) compression of a dressing with differentforce applied. It can be seen that for almost all forces applied (apartfrom the extreme ends of the scale at 0 to 3 kgf (kilogram-force) and 40kgf and over where readings show no appreciable difference), dressingcompression is higher for a dressing formed from foam only having athickness of 4 mm, such as the foam materials described for layer 103(curve a) than for a dressing including a foam layer of thickness 2 mmand a fibrous non-woven material, such as the materials described forlayer 105 (curve b) and a dressing including a foam layer of thickness 2mm and a fibrous non-woven material, such as the materials described forlayer 105, and a layer of 3-D knit material such as the materialsdescribed for layer 106 (curve c). As can be seen from the graph in FIG.9, dressing including a layer of 3-D knit material (curve c) gave thelowest percentage compression of dressing over the range of forcesapplied between 3 kg and 40 kg.

From this it can be concluded that fibrous non-woven materials and 3-Dknit materials will help to act against a force applied by dissipatingthe force and preventing compression of the dressing.

FIG. 10 illustrates the area over which pressure is transferred bydifferent dressings when pressure is applied to the dressing from thepoint pressure of a 0.8 cm² probe. The area of pressure transferred wasmeasured using a pressure reading mat. This equipment was obtained fromTekscan, and includes an array of thin pressure sensors placed betweentwo relatively thin sheets of plastic. The resulting mat is conformable,and transmits pressure readings from the array through a piece ofhardware (I-scan handle), to a computer equipped with the I-scansoftware. The resulting measurements can be expressed for example ascontour maps, value tables, maximum pressure reading for a particulararea of the mat, average pressure read over the whole testing area, orcontact area over which a pressure was sensed by the mat. Pressuretransfer was measured on a dressing including a layer of 3-D knitmaterial (identical to the dressing used giving curve c in FIG. 9)(column 1), a dressing made of non-woven material (identical to thedressing used giving curve b in FIG. 9) (column 2) and a foam dressing(identical to the dressing used giving curve a in FIG. 9) (column 3).

FIG. 13 illustrates tests performed by the inventors on four differentwound dressings including a dressing as described above with respect toFIG. 1 (column A). Columns B, C and D show the results for other foamdressings. The graph represents the average pressure measured underneatha dressing (as measured by a Tekscan pressure reading mat and softwareas described above) when the upper surface of the dressing (non-woundcontacting side) is impacted at a speed of 3 m/min by a probe until apressure of 735 mmHg is applied. The area of pressure application was a10 mm diameter cylindrical probe, onto which a rubber ball of 6.5 cmdiameter was attached. It is estimated that the area over which therubber ball contacted the top of the dressing was 3% of the total areaof the rubber sphere, that is 4 cm². This can be compared to acylindrical probe of diameter 2.25 cm. A summary of the pressuretransferred and the area over which pressure was transferred is shown inTable 1 below.

TABLE 1 Estimated area over Average pressure which pressure is Sampletransferred (mmHg) transferred (cm²) Pressure applied 735 4 Dressing ofFIG. 1 (A) 25 12.3 Dressing B (foam 39 10.6 composite) Dressing C (foam)36 11.7 Dressing D (foam) 31 117

Preferably the dressing area to be tested is of 20 cm² or more whenusing a cylindrical probe of 10 mm diameter, to ensure that the probesize is not larger than the test sample and to ensure pressure isredistributed efficiently through the sample.

Aptly the pressure spreading layer increases the area over whichpressure is transferred by at least 25% of the initial application areaand more aptly by at least 50% of the initial application area.

The inventors have found that a combination of materials may, as acomposite, increase the area over which pressure is transferred by atleast 50%, aptly at least 100%, more aptly at least 200% of the initialapplication area. An increase in the area over which pressure istransferred of 200%.

Individual components can also be assessed for pressure redistributionfrom a static test, where a pressure of 736 mmHg is applied staticallyto various materials. Values obtained are shown in the table below:

TABLE 2 Area over which Average pressure pressure is Sample transferred(mmHg) transferred (cm2) Pressure applied 736 0.8 Foam 301 1.2Superabsorbent 198 1.8 layer 3D fabric #1 249 1.5 3D fabric #2 173 n/aComposite dressing 53 6.4

The above-described tests on pressure dissipation suggest that adressing including a shielding layer such as a 3-D spacer layer andoptionally also an absorbent layer give enhanced performance in terms ofspreading a pressure applied, and thus should perform better againstaccidental knocks to the wound site for example, compared to knowndressings.

The inventors also performed tests upon various dressings with respectto the masking properties of the dressing. The ability to mask colourmay be calculated, for example, by measuring the reduction in absorptionof light radiation at particular wavelengths. FIG. 14 illustrates theabsorption at various different wavelengths of 3 different samples. Thetests utilized a UV-Vis spectrophotometer Jasco with integrating sphere,with a scanning range 340 to 800 nm, bandwidth 5 nm and 1000 nm/secscanning speed. The data labelled black background represents theextreme of exudate colour (the most colour an exudate might have)—thehighest level of radiation absorbed and the least amount of radiationreflected from the sample. The data for white background represents theupper limit for total masking—generally the lowest level of radiationabsorbed and the highest level of reflection. Sample 1 was a tintedpolymer film placed over a black background, which was judged not tosufficiently mask the black background (representing wound exudate)satisfactorily. Sample 2 was a sheet of 3-dimensional spacer fabric(Baltex 3D) placed over a black background, and was judged to provideadequate masking of the black background. Sample 3 was a sheet ofnon-woven material dyed green placed over a black background, andprovided complete masking of the black background.

The inventors noted that any wound exudate may have dark yellow, redand/or brown tones. Therefore, to appropriately mask these colours, amasking layer would need to shield light wavelengths of below 600 nm.

Measuring the reduction in absorption of light radiation at particularwavelengths may be performed by calculating:% reduction=(A _(background) −A _(sample placed on background))/(A_(background))×100where A is the absorption of light radiation at the particularwavelength.

Using this formula, using light at a wavelength of 460 nm, thepercentage of absorption reduction was calculated as shown in Table 3below.

TABLE 3 Appropriate masking Sample Absorption reduction at 460 nmobserved Sample 1 34% No Sample 2 77% Yes - partial Sample 3 69% Yes -complete

It has been found that materials that reduce light absorption by about50% or more will provide enough partial or complete masking of woundexudate (as judged by the inventors). Of course a complete maskingelement wound preferably require a means for a clinician to judge thespread of wound exudate in the dressing below the masking element, e.g.the masking element not completely covering the entire dressing.Alternatively a partial masking element may allow a clinician to judgethe spread of exudate in the dressing below without additional means.

It will be understood that the wetting of a masking material (by exudatefor example) will also affect the masking performance of the maskingelement, since hydrophilic materials will allow chromophore-carryingspecies to travel through them more easily. As such, the absorptionreduction rate should also be tested on wet materials.

The inventors also tested the above-mentioned Samples 1, 2 and 3 fortheir masking properties by measuring CIE L*a*b* values (a known3-dimensional model for representing colour space). The analysisemployed Jasco software using the range 380 to 780 nm, stard observed2(deg), lightsource D65, colour matching JIS Z8701-1999.

Table 4 below shows the L*a*b* values found when Samples 1, 2 and 3 wererespectively placed over a black background. The results for the blackbackground alone and a white background are also shown.

TABLE 4 Appropriate CIE L*a*b* values recorded masking Sample L* a* b*observed? Black 0 0 0 n/a background Sample 1 (on 36.59 3.76 −1.80 Noblack) Sample 2 (on 71.76 −0.20 −1.08 Yes - partial black) Sample 3 (on70.64 −0.25 −1.23 Yes - complete black) White 100 0 0 n/a background

Generally, samples which lead to an increase in L* value will provide alighter colour tone than the reference surface, which is the maincontributor to masking a dark colour. From the values above, apt partialmasking materials will yield an L* value above 50, or more aptly above70.

However, completely opaque masking layers, such as for example a tintedpolymeric film, may cover the area to be masked with a darker tonealtogether, in which case the measure of L* is not relevant.

Once again these values should also be considered on wet material, forthe reasons stated above.

In addition, the dressing of the disclosure may be arranged to preventshear stress between layers from causing damage to the dressing. This isbecause the layers are generally not adhered together, other than thetop film 102 and wound contact layer 101 being adhered in the borderregion 110. Thus even if friction or other energy from shear movementoccurs, the energy is dissipated by the layers prior to reaching thepatient.

The wound facing surface of a wound dressing may be provided with arelease coated protector (not shown in the figures), for example asilicon-coated paper. The protector covers the wound contacting side ofthe dressing prior to application to a patient, and can be peeled awayat the time of use.

Various modifications to the detailed arrangements as described aboveare possible. For example, dressings according to the present disclosuredo not require each of the specific layers as described above withrespect to FIG. 1. Dressings may include only one layer, or anycombination of the layers described above. Alternatively oradditionally, the materials of the layers described above may becombined into a single layer or sheet of material to perform thefunctions of each layer by a single layer.

As noted above, each of the layers described may be used to give one ormore function to the wound dressing. As such, each of the layermaterials may be used separately or in any combination such that eachmaterial provides the given function.

The wound contact layer described above is an optional layer. If used, awound contact layer may be of any suitable material, such aspolyethylene (or polyurethane as described above) or other suitablepolymer, and may be perforated for example by a hot pin process, laserablation process, ultrasound process or in some other way so as to bepermeable to fluids.

Although the dressing described above has been described having a borderregion and a central region this need not be the case. The dressing maybe provided without an adhesive layer for attachment to the skin of apatient. Rather, another means may be provided for locating the dressingat the correct position over a wound, such as adhesive tape or a tiedbandage.

The relative widths of the various layers may be all the same ordifferent to those as shown in the figures.

The dressing pad assembly may optionally be arranged with layers so thatodour control is placed between two layers of different rates ofabsorptions. The odour control layer can be a charcoal cloth (knitted,woven, felt, non-woven), or any other textile, foam, gel, net or meshimpregnated with odour-control materials. Such odour control materialscan be cyclodextrins, zeolites, ion-exchange resins, oxidising agents,activated charcoal powder. It is also possible to use said odour-controlmaterials dispersed in any layer of the pad assembly, and not as adiscrete layer.

The dressing may optionally include a means of partially obscuring thetop surface. This could also be achieved using a textile (knitted,woven, or non-woven) layer without openings, provided it still enablesfluid evaporation from the absorbent structure. It could also beachieved by printing a masking pattern on the top film, or on the topsurface of the uppermost pad component, using an appropriate ink orcoloured pad component (yarn, thread, coating) respectively. Another wayof achieving this would be to have a completely opaque top surface,which could be temporarily opened by the clinician for inspection of thedressing state (for example through a window), and closed again withoutcompromising the environment of the wound.

The dressing may optionally be arranged such that it has enhancedcompatibility with body movement. This could also be achieved using adifferent shape for the sub-areas, such as diamonds, triangles, or aplurality of such shapes tessellated across the area of the dressing.Alternatively, preferential folding lines may be scored within thethickness of the dressing material, and thus define independentsub-areas for adapting to movement. Alternatively, the layers could bebonded using an elastic material, such as a viscoelastic adhesive, whichwould allow shear between the layers but refrain them from becomingseparated and shifting across the pad.

A dressing may optionally be arranged that provides enhanced protectionagainst mechanical forces. Other ways of achieving this include:

-   -   Incorporation of pressure-relieving components within other        layers of the dressing, such as within the foam layer (e.g.        moulding the foam around a 3-D structure capable of spreading        load)    -   Incorporation of pressure-absorbing component within other        layers of the dressing (e.g. beads of viscoelastic material        incorporated in the superabsorbent layer)

A dressing assembly may optionally be arranged where the flowingproperties are being provided by given material layers, and where therespective position of these layers provides additional properties ontop of those from the individual layers. Alternative arrangement oflayers than that described above may still provide some of theproperties sought.

For example, placing the shielding layer (106) below the superabsorbentlayer (105) would still allow protection from point pressure, but wouldlose the masking ability of this layer, and would probably affect thetransmission of fluid between the foam layer (103) and thesuperabsorbent layer (105).

Another example is the placement of the odour control layer or componentfurther away from the wound: this can be seen as beneficial because sometypes of odour control work differently depending on whether they arewet or dry. Placing a colour-less odour control component towards thetop of the dressing (anywhere above (105)) could provide odour controlproperties without the visual impact that a black layer of charcoalcloth would have.

It can also be envisaged that several properties are combined within onelayer, for example superabsorbent and odour control components could beincorporated in the foam structure. The only remaining optionalproperties to provide in this case would be protection and masking,which could be achieved by placing a layer (106) directly above such amodified foam if needed.

Interestingly, the fluid handling properties of an embodiment where thesuperabsorbing function is located within the lowest part of thedressing pad may not be as beneficial as those of an embodiment wherethe functions are held in separate layers, and the fluid is directedfrom one layer to another.

In another embodiment, the shielding layer 106 is of the same dimensionsas 105, and clinical judgment of the exudate spread can be made byobserving the spread of exudate through the masking layer. Thisembodiment has the advantage of completely masking unsightly exudatefrom the superabsorbent layer.

Alternatively or additionally, the shielding layer can be provided withfull masking capability, and windows provided at discrete points of thelayer for enabling judgement of the exudate spread below such layer.Examples of such windows are illustrated in FIGS. 12 a and 12 b. Thedressing 1200 shown in FIG. 12a includes a masking layer 1202 andcrescent-shaped windows 1204 provided in the masking layer to extendthrough the layer allowing visibility of the dressing therebelow. Thedressing 1210 of FIG. 12b includes a masking layer 1212 and a number ofholes 1214 therethrough acting as windows for viewing the state of thedressing therebelow. FIG. 12c shows another dressing 1220 including amasking layer 1222 with windows 1224. With the dressings 1200,1210,1220the progress of exudate spread over the dressing and towards the edge ofthe dressing can be monitored. In other alternatives instructions may begiven to change the dressing when the exudate reaches a predetermineddistance from the edge of the dressing, such as 5 mm from the dressingedge or 7 mm from the dressing edge, etc. Alternatively a ‘trafficlight’ system may be implemented whereby an electronic indicator showsgreen, amber or red light to indicate the spread of exudate in thedressing. Alternatively or additionally, another suitable indicator maybe used for indicating the spread of exudate over the dressing.

In another embodiment, odour control is not provided by a separate layer(i.e. no layer 104), but instead the odour-control material (activatedcharcoal, cyclodextrin, ion exchange resin, or other) is dispersedthroughout another layer. This can be envisaged within the foam (103),the superabsorbent structure (105), or as a coating onto the maskinglayer (106).

In addition or alternatively, the obscuring layer may be coated with orformed from a material with size-exclusion properties to help withmasking the exudate from view. For example, such a layer could have itslowermost side (the side closer to the wound) coated with materials suchas zeolites or clays such as bentonite or sepiolite (the charged surfaceof which will tend to attract proteins and protein derivativescontaining chromophores), other inorganic powders or molecular sieves(e.g. amberlite), proteins (albumin, haemoglobin components withmolecular weight 15 to 70 KDa), ionic complexes such as hemes (molecularweight 600 to 850 g/mol), which have the function of immobilisingspecies above a certain size or molecular weight. For example, specieshaving molecular weight above 100 g/mol.

The shielding layer may be coated with or be formed of a hydrophiliccompound (e.g. polyesters, polyurethanes, polyureas, polysaccharides,etc.) for assisting in wicking moisture towards the surface of thedressing, helping breathability of the dressing.

The shielding layer may be combined with a cover layer, such as anopaque or dark pigmented top layer.

The shielding layer (acting as a masking layer) may be combined with anabsorbent layer, for example by providing an absorbent layer that hasbeen dyed, for example with a dark blue pigment to the fibres of anon-woven or airlaid material.

The shielding layer (acting as a pressure relieving layer) may becombined with an absorbent layer. For example a fibrous superabsorberlayer may be provided with a high density of fibres for spreading pointpressure. Alternatively a hydrophilic foam may be moulded aroundpressure-redistributing structures of pillars or arrays of an elastomermaterial, for example.

Odour control can be combined with absorbency by dispersing particles ofactivated charcoal or other odour-catching material in a hydrophilicfoam at time of reaction, or dispersing it throughout an air-laidmaterial as a powder, or introducing it in the master batch of absorbentpolymer used to manufacture fibres which will then be used in anair-laid.

As such, odour control, absorbency and pressure redistribution could beincluded in a single layer, and if this material was dyed, masking couldalso be performed.

The layers described herein may each be provided directly adjacentanother layer or with further layers therebetween.

A wound dressing may be formed by bringing together a layer of absorbentmaterial with a layer of obscuring material.

Alternatively a wound dressing may be formed by bringing together alayer of absorbent material with a layer of protective material.

Alternatively a wound dressing may be formed by bringing together alayer of absorbent material with a cover layer.

Alternatively a wound dressing may be formed by bringing together alayer of absorbent material with a fluid transmission layer with a layerof activated charcoal material therebetween.

Any of the methods above may include bringing layers together withadhesive over part or all of a layer. The method may be a laminationprocess.

Alternatively a wound dressing may be formed by bringing together layersas described with respect to FIG. 1, in a contiguous laminar stack, andadhering the top film to the wound contact layer in a border region.

Alternatively a wound dressing may be formed by forming a sheet ofmaterial for absorbing wound exudate, the sheet comprising at least oneof a foam, an odour capturing material, an absorbent material, and ashielding material for masking or pressure spreading.

The dressing of the disclosure may be manufactured by continuousproduction techniques. For example, a sheet or sheets of suitablematerial may be run through rollers to enable the adhesion of one layerto another. Alternatively, pre-cut pad component shapes can be placedonto a web of one of the adhesive film or net components, before beingencapsulated by the another adhesive film or net component. Then thedressing may be stamped out by cutting through the material in thedesired shape and packaged.

In use, a wound dressing of the present disclosure would be applied to awound site of a patient with the surface of the wound contacting side ofthe dressing facing the wound site. The wound dressing would then bemonitored over a predetermined time period to assess the extent ofexudate present in the dressing. The dressing may be any of the examplesand embodiments described herein.

The dressing may be monitored at predetermined intervals or atpredetermined time(s) of the day. For example, the dressing may bemonitored every 6 hours, or once every morning, lunchtime and evening,for example, or as required by the specific patient.

A method for determining the saturation of a wound dressing with woundexudate comprises:

-   -   viewing a wound dressing at predetermined intervals to assess        the extent of exudate present in the wound dressing.

The dressing may be any of the dressings described herein.

With the above-described arrangements one or more advantages over knowndressings may be achieved.

The disclosure described contains elements which lead to a combinationof properties that is not currently being met by existing devices.

In particular, the combination of an effective odour-control layer, heldbetween two absorbent layers of differential absorption power, yields anabsorbent structure which does not require a barrier layer to remainefficient against odours.

The odour-removing layer is not bonded to adjacent layers. Because ofthis, the available surface area of active pores of the odour layer isnot diminished. That is, in known dressings including an odour resistantlayer of activated charcoal, the material is carbonised to insert carboninto the surface porosity of the layer. The layer is then adhered to anadjacent layer, thus coating some of the porous surface area withadhesive, and reducing the total surface porosity.

The present disclosure comprising a shaped pad and dressing border,working as more independent sub-units of the dressing than what can beseen for a standard square shape, yields better conformability withmovement than standard shapes. The dressing remains conformable with theskin and comfortable to wear, allowing the patient to move whilstwearing the dressing, and without creating detrimental traction on theperi-wound skin, which could lead to slowing of wound healing.

Some embodiments of the present disclosure also help to reduce theunsightly appearance of a dressing during use, by using materials thatimpart partial masking of the dressing surface. The masking shouldpreferably only be partial, to allow clinicians to access theinformation they require by observing the spread of exudate across thedressing surface. This property, which is very important in helpingpatients live better with their treatment, had not been achieved untilnow for absorbent, breathable dressings. The partial masking nature ofthe obscuring layer enables a skilled clinician to perceive a differentcolour caused by exudate, blood, by-products etc. in the dressingallowing for a visual assessment and monitoring of the extent of spreadacross the dressing. However, since the change in colour of the dressingfrom its clean state to a state with exudate contained is only a slightchange, the patient is unlikely to notice any aesthetic difference.Reducing or eliminating a visual indicator of wound exudate from apatient is likely to have a positive effect on their health, reducingstress for example. Also, some embodiments of the present disclosureprovide a mean of relieving point pressure that may be applied to thewound area, by introducing a breathable, shear resistant layer that doesnot have to be in contact with the skin. This construction maximises theabsorbency capacity of the dressing by not replacing some of theabsorbent area with pressure-relieving areas. Breathability of the partof the dressing in contact with the skin is also maximise, as thebreathable wound contact layer, lower part of the pad, and film, are notimpaired by the use of another structure in contact with the skin.

By providing an odour control layer between a foam and an absorberlayer, this can help in allowing only excess fluid towards the absorberlayer, whilst keeping the foam layer sufficiently moist to create amoist wound healing environment. This is because the odour layer doesnot draw fluid away from the foam layer at the same speed at which anabsorbent layer would. The transfer of fluid from the foam layer to theabsorbent layer is therefore slowed down (relative to having a foamlayer directly adjacent an absorber layer). Therefore, only excess fluidis taken into the odour layer, thereby assisting in the foam layermaintaining some degree of moisture and not drying out.

That is, the absorption rate of the outer layer should aptly be higherthan the absorption rate of the lower layer (closer to the wound).

Prior to the invention of the embodiments disclosed herein, it wasgenerally believed that the wetting of activated charcoal would destroythe function of the material of performing odour capturing. As such,activated charcoal layers have been used as an outer layer protectedfrom liquid by a barrier layer. However the inventors found that as longas the activated charcoal layer is not soaked in liquid the activatedcharcoal can perform sufficiently well as an odour removing layer.

When the layer of absorbent material folds over the edges of any otherlower layers, the absorbent layer helps to prevent fluid from beingsqueezed from the dressing at the dressing edge region, thereby causingleakage. Various known dressings previously suffered from the risk ofdelamination of layers caused by fluid being squeezed towards the edgeof the dressing, being driven between the layers and possibly escapingat the edge of the dressing. This may occur for example in a borderregion where a wound contact layer meets a cover layer, and anyintermediate layers of the dressing are adjacent that border region.Aptly an absorbent layer including a superabsorber material is useful inpreventing the release of any liquid, especially in the direction of theborder region or edge of the dressing.

Alternative materials can be used for the absorbent layer to provide thefluid locking and leak prevention properties, for example:

-   -   absorbent or superabsorbent non-woven materials, which can be        made of fibrous modified cellulose, fibrous modified chitosan,        fibrous hydrophilic polyesters, fibrous cellulose, fibrous        chitosan, fibrous polysaccharides    -   absorbent or superabsorbent foams, which can be blown        hydrophilic polyurethane foam, comprising superabsorbent        particles or fibres; foams of hydrophilic polyvinylacetate

absorbent or superabsorbent gels or solids, which can be hydrocolloidpolymer structures, additionally comprising superabsorbent particles orfibres.

Additionally, any of the dressing embodiments disclosed herein can beused in with a source of negative pressure, such as a pump. Any of thedressing embodiments disclosed herein can also be used with a pump and afluid or waste collection canister that can be put in fluidcommunication with the pump and the dressing so that the pump drawsfluid or waste from the wound into the collection canister.

Additionally, in any embodiments, the pump can be a piezoelectric pump,a diaphragm pump, a voice coil actuated pump, a constant tension springactuated pump, a manually actuated or operated pump, a battery poweredpump, a DC or AC motor actuated pump, a combination of any of theforegoing, or any other suitable pump.

FIGS. 15A-B illustrate cross sections through a wound dressing 2100according to an embodiment of the disclosure. A plan view from above thewound dressing 2100 is illustrated in FIG. 16 with the line A-Aindicating the location of the cross section shown in FIGS. 15A and 15B.It will be understood that FIGS. 15A-B illustrate a generalizedschematic view of an apparatus 2100. It will be understood thatembodiments of the present disclosure are generally applicable to use inTNP therapy systems. Briefly, negative pressure wound therapy assists inthe closure and healing of many forms of “hard to heal” wounds byreducing tissue oedema; encouraging blood flow and granular tissueformation; removing excess exudate and may reduce bacterial load (andthus infection risk). In addition, the therapy allows for lessdisturbance of a wound leading to more rapid healing. TNP therapysystems may also assist on the healing of surgically closed wounds byremoving fluid and by helping to stabilize the tissue in the apposedposition of closure. A further beneficial use of TNP therapy can befound in grafts and flaps where removal of excess fluid is important andclose proximity of the graft to tissue is required in order to ensuretissue viability.

The wound dressing 2100, which can alternatively be any wound dressingembodiment disclosed herein including without limitation wound dressing100 or have any combination of features of any number of wound dressingembodiments disclosed herein, can be located over a wound site to betreated. The dressing 2100 forms a sealed cavity over the wound site. Itwill be appreciated that throughout this specification reference is madeto a wound. In this sense it is to be understood that the term wound isto be broadly construed and encompasses open and closed wounds in whichskin is torn, cut or punctured or where trauma causes a contusion. Awound is thus broadly defined as any damaged region of tissue wherefluid may or may not be produced. Examples of such wounds include, butare not limited to, incisions, lacerations, abrasions, contusions,burns, diabetic ulcers, pressure ulcers, stoma, surgical wounds, traumaand venous ulcers or the like.

In some embodiments, it may be preferable for the wound site to befilled partially or completely with a wound packing material. This woundpacking material is optional, but may be desirable in certain wounds,for example deeper wounds. The wound packing material can be used inaddition to the wound dressing 2100. The wound packing materialgenerally may comprise a porous and conformable material, for examplefoam (including reticulated foams), and gauze. Preferably, the woundpacking material is sized or shaped to fit within the wound site so asto fill any empty spaces. The wound dressing 2100 may then be placedover the wound site and wound packing material overlying the wound site.When a wound packing material is used, once the wound dressing 2100 issealed over the wound site, TNP is transmitted from a pump through thewound dressing 2100, through the wound packing material, and to thewound site. This negative pressure draws wound exudate and other fluidsor secretions away from the wound site.

It is envisaged that the negative pressure range for the apparatusembodying the present disclosure may be between about −20 mmHg and −200mmHg (note that these pressures are relative to normal ambientatmospheric pressure thus, −200 mmHg would be about 560 mmHg inpractical terms). In one embodiment, the pressure range may be betweenabout −40 mmHg and −150 mmHg. Alternatively a pressure range of up to−75 mmHg, up to −80 mmHg or over −80 mmHg can be used. Also in otherembodiments a pressure range of below −75 mmHg could be used.Alternatively a pressure range of over −100 mmHg could be used or over−150 mmHg.

It will be appreciated that according to certain embodiments of thepresent disclosure, the pressure provided may be modulated over a periodof time according to one or more desired and predefined pressureprofiles. For example such a profile may include modulating the negativepressure between two predetermined negative pressures P1 and P2 suchthat pressure is held substantially constant at P1 for a pre-determinedtime period T1 and then adjusted by suitable means such as varying pumpwork or restricting fluid flow or the like, to a new predeterminedpressure P2 where the pressure may be held substantially constant for afurther predetermined time period T2. Two, three or four or morepredetermined pressure values and respective time periods may beoptionally utilized. Other embodiments may employ more complexamplitude/frequency wave forms of pressure flow profiles may also beprovided e.g. sinusoidal, sore tooth, systolic-diastolic or the like.

As illustrated in FIGS. 15A-B a lower surface 2101 of the wound dressing2100, which, again, can be any wound dressing embodiment disclosedherein including without limitation dressing embodiment 100 or have anycombination of features of any number of wound dressing embodimentsdisclosed herein, can be provided by an optional wound contact layer2102. The wound contact layer 2102 can be a polyurethane layer orpolyethylene layer or other flexible layer which is perforated, forexample via a hot pin process, laser ablation process, ultrasoundprocess or in some other way or otherwise made permeable to liquid andgas. The wound contact layer has a lower surface 2101 and an uppersurface 2103. The perforations 2104 are through holes in the woundcontact layer which enables fluid to flow through the layer. The woundcontact layer helps prevent tissue ingrowth into the other material ofthe wound dressing. The perforations are small enough to meet thisrequirement but still allow fluid through. For example, perforationsformed as slits or holes having a size ranging from 0.025 mm to 1.2 mmare considered small enough to help prevent tissue ingrowth into thewound dressing while allowing wound exudate to flow into the dressing.The wound contact layer helps hold the whole wound dressing together andhelps to create an air tight seal around the absorbent pad in order tomaintain negative pressure at the wound. The wound contact layer alsoacts as a carrier for an optional lower and upper adhesive layer (notshown). For example, a lower pressure sensitive adhesive may be providedon the underside surface 2101 of the wound dressing whilst an upperpressure sensitive adhesive layer may be provided on the upper surface2103 of the wound contact layer. The pressure sensitive adhesive, whichmay be a silicone, hot melt, hydrocolloid or acrylic based adhesive orother such adhesives, may be formed on both sides or optionally on aselected one or none of the sides of the wound contact layer. When alower pressure sensitive adhesive layer is utilized this helps adherethe wound dressing to the skin around a wound site.

A layer 2105 of porous material can be located above the wound contactlayer. This porous layer, or transmission layer, 2105 allowstransmission of fluid including liquid and gas away from a wound siteinto upper layers of the wound dressing. In particular, the transmissionlayer 2105 ensures that an open air channel can be maintained tocommunicate negative pressure over the wound area even when theabsorbent layer has absorbed substantial amounts of exudates. The layershould remain open under the typical pressures that will be appliedduring negative pressure wound therapy as described above, so that thewhole wound site sees an equalized negative pressure. The layer 2105 isformed of a material having a three dimensional structure. For example,a knitted or woven spacer fabric (for example Baltex 7970 weft knittedpolyester) or a non-woven fabric could be used. Other materials could ofcourse be utilized, and examples of such materials are described belowwith respect to FIGS. 37-41.

In some embodiments, the transmission layer comprises a 3D polyesterspacer fabric layer including a top layer (that is to say, a layerdistal from the wound-bed in use) which is a 84/144 textured polyester,and a bottom layer (that is to say, a layer which lies proximate to thewound bed in use) which is a 100 denier flat polyester and a third layerformed sandwiched between these two layers which is a region defined bya knitted polyester viscose, cellulose or the like monofilament fiber.Other materials and other linear mass densities of fiber could of coursebe used.

Whilst reference is made throughout this disclosure to a monofilamentfiber it will be appreciated that a multistrand alternative could ofcourse be utilized.

The top spacer fabric thus has more filaments in a yarn used to form itthan the number of filaments making up the yarn used to form the bottomspacer fabric layer.

This differential between filament counts in the spaced apart layershelps control moisture flow across the transmission layer. Particularly,by having a filament count greater in the top layer, that is to say, thetop layer is made from a yarn having more filaments than the yarn usedin the bottom layer, liquid tends to be wicked along the top layer morethan the bottom layer. In use, this differential tends to draw liquidaway from the wound bed and into a central region of the dressing wherethe absorbent layer helps lock the liquid away or itself wicks theliquid onwards towards the cover layer where it can be transpired.

Preferably, to improve the liquid flow across the transmission layer(that is to say perpendicular to the channel region formed between thetop and bottom spacer layers, the 3D fabric is treated with a drycleaning agent (such as, but not limited to, Perchloro Ethylene) to helpremove any manufacturing products such as mineral oils, fats and/orwaxes used previously which might interfere with the hydrophiliccapabilities of the transmission layer. In some embodiments, anadditional manufacturing step can subsequently be carried in which the3D spacer fabric is washed in a hydrophilic agent (such as, but notlimited to, Feran Ice 30 g/l available from the Rudolph Group). Thisprocess step helps ensure that the surface tension on the materials isso low that liquid such as water can enter the fabric as soon as itcontacts the 3D knit fabric. This also aids in controlling the flow ofthe liquid insult component of any exudates.

A layer 2110 of absorbent material is provided above the transmissionlayer 2105.

The absorbent material which may be a foam or non-woven natural orsynthetic material and which may optionally include or besuper-absorbent material forms a reservoir for fluid, particularlyliquid, removed from the wound site and draws those fluids towards acover layer 2140. With reference to FIGS. 15A and 15B, a masking orobscuring layer 2107 can be positioned beneath the cover layer 2140. Insome embodiments, the masking layer 2107 can have any of the samefeatures, materials, or other details of any of the other embodiments ofthe masking layers disclosed herein, including but not limited to havingany viewing windows or holes. Additionally, the masking layer 2107 canbe positioned adjacent to the cover layer, or can be positioned adjacentto any other dressing layer desired. In some embodiments, the maskinglayer 2107 can be adhered to or integrally formed with the cover layer.

The material of the absorbent layer also prevents liquid collected inthe wound dressing from flowing in a sloshing manner. The absorbentlayer 2110 also helps distribute fluid throughout the layer via awicking action so that fluid is drawn from the wound site and storedthroughout the absorbent layer. This helps prevent agglomeration inareas of the absorbent layer. The capacity of the absorbent materialmust be sufficient to manage the exudates flow rate of a wound whennegative pressure is applied. Since in use the absorbent layerexperiences negative pressures the material of the absorbent layer ischosen to absorb liquid under such circumstances. A number of materialsexist that are able to absorb liquid when under negative pressure, forexample superabsorber material. The absorbent layer 2110 may typicallybe manufactured from ALLEVYN™ foam, Freudenberg 114-224-4 and/orChem-Posite™11C-450.

In some embodiments, the absorbent layer is a layer of non-wovencellulose fibers having super-absorbent material in the form of dryparticles dispersed throughout. Use of the cellulose fibers introducesfast wicking elements which help quickly and evenly distribute liquidtaken up by the dressing. The juxtaposition of multiple strand-likefibers leads to strong capillary action in the fibrous pad which helpsdistribute liquid. In this way, the super-absorbent material isefficiently supplied with liquid. Also, all regions of the absorbentlayer are provided with liquid.

The wicking action also assists in bringing liquid into contact with theupper cover layer to aid increase transpiration rates of the dressing.

The wicking action also assists in delivering liquid downwards towardsthe wound bed when exudation slows or halts. This delivery process helpsmaintain the transmission layer and lower wound bed region in a moiststate which helps prevent crusting within the dressing (which could leadto blockage) and helps maintain an environment optimized for woundhealing.

In some embodiments, the absorbent layer may be an air-laid material.Heat fusible fibers may optionally be used to assist in holding thestructure of the pad together. It will be appreciated that rather thanusing super-absorbing particles or in addition to such use,super-absorbing fibers may be utilized according to certain embodimentsof the present disclosure. An example of a suitable material is theProduct Chem-Posite™ 11 C available from Emerging Technologies Inc (ETi)in the USA.

Optionally, according to certain embodiments of the present disclosure,the absorbent layer may include synthetic stable fibers and/orbi-component stable fibers and/or natural stable fibers and/orsuper-absorbent fibers. Fibers in the absorbent layer may be securedtogether by latex bonding or thermal bonding or hydrogen bonding or acombination of any bonding technique or other securing mechanism. Insome embodiments, the absorbent layer is formed by fibers which operateto lock super-absorbent particles within the absorbent layer. This helpsensure that super-absorbent particles do not move external to theabsorbent layer and towards an underlying wound bed. This isparticularly helpful because when negative pressure is applied there isa tendency for the absorbent pad to collapse downwards and this actionwould push super-absorbent particle matter into a direction towards thewound bed if they were not locked away by the fibrous structure of theabsorbent layer.

The absorbent layer may comprise a layer of multiple fibers. Preferably,the fibers are strand-like and made from cellulose, polyester, viscoseor the like. Preferably, dry absorbent particles are distributedthroughout the absorbent layer ready for use. In some embodiments, theabsorbent layer comprises a pad of cellulose fibers and a plurality ofsuper absorbent particles. In additional embodiments, the absorbentlayer is a non-woven layer of randomly orientated cellulose fibers.

Super-absorber particles/fibers may be, for example, sodium polyacrylateor carbomethoxycellulose materials or the like or any material capableof absorbing many times its own weight in liquid. In some embodiments,the material can absorb more than five times its own weight of 0.9% W/Wsaline, etc. In some embodiments, the material can absorb more than 15times its own weight of 0.9% W/W saline, etc. In some embodiments, thematerial is capable of absorbing more than 20 times its own weight of0.9% W/W saline, etc. Preferably, the material is capable of absorbingmore than 30 times its own weight of 0.9% W/W saline, etc.

Preferably, the particles of superabsorber are very hydrophilic and grabthe fluid as it enters the dressing, swelling up on contact. Anequilibrium is set up within the dressing core whereby moisture passesfrom the superabsorber into the dryer surrounding area and as it hitsthe top film the film switches and the fluid vapor starts to betranspired. A moisture gradient is established within the dressing tocontinually remove fluid from the wound bed and ensure the dressing doesnot become heavy with exudate.

Preferably the absorbent layer includes at least one through holelocated so as to underly the suction port. As illustrated in FIGS. 15A-Ba single through hole can be used to produce an opening underlying theport 2150. It will be appreciated that multiple openings couldalternatively be utilized. Additionally should more than one port beutilized according to certain embodiments of the present disclosure oneor multiple openings may be made in the super-absorbent layer inregistration with each respective port. Although not essential tocertain embodiments of the present disclosure the use of through holesin the super-absorbent layer provide a fluid flow pathway which isparticularly unhindered and this is useful in certain circumstances.

Where an opening is provided in the absorbent layer the thickness of thelayer itself will act as a stand-off separating any overlying layer fromthe upper surface (that is to say the surface facing away from a woundin use) of the transmission layer 2105. An advantage of this is that thefilter of the port is thus decoupled from the material of thetransmission layer. This helps reduce the likelihood that the filterwill be wetted out and thus will occlude and block further operation.

Use of one or more through holes in the absorption layer also has theadvantage that during use if the absorbent layer contains a gel formingmaterial, such as superabsorber, that material as it expands to absorbliquid, does not form a barrier through which further liquid movementand fluid movement in general cannot pass. In this way each opening inthe absorbent layer provides a fluid pathway between the transmissionlayer directly to the wound facing surface of the filter and thenonwards into the interior of the port.

A gas impermeable, but moisture vapor permeable, cover layer 2140 canextend across the width of the wound dressing, which can be any wounddressing embodiment disclosed herein including without limitationdressing embodiment 100 or have any combination of features of anynumber of wound dressing embodiments disclosed herein. The cover layer,which may for example be a polyurethane film (for example, ElastollanSP9109) having a pressure sensitive adhesive on one side, is impermeableto gas and this layer thus operates to cover the wound and to seal awound cavity over which the wound dressing is placed. In this way aneffective chamber is made between the cover layer and a wound site wherea negative pressure can be established. The cover layer 2140 is sealedto the wound contact layer 2102 in a border region 2200 around thecircumference of the dressing, ensuring that no air is drawn in throughthe border area, for example via adhesive or welding techniques. Thecover layer 140 protects the wound from external bacterial contamination(bacterial barrier) and allows liquid from wound exudates to betransferred through the layer and evaporated from the film outersurface. The cover layer 2140 typically comprises two layers; apolyurethane film and an adhesive pattern spread onto the film. Thepolyurethane film is moisture vapor permeable and may be manufacturedfrom a material that has an increased water transmission rate when wet.

The absorbent layer 2110 may be of a greater area than the transmissionlayer 2105, such that the absorbent layer overlaps the edges of thetransmission layer 2105, thereby ensuring that the transmission layerdoes not contact the cover layer 2140. This provides an outer channel2115 of the absorbent layer 2110 that is in direct contact with thewound contact layer 2102, which aids more rapid absorption of exudatesto the absorbent layer. Furthermore, this outer channel 2115 ensuresthat no liquid is able to pool around the circumference of the woundcavity, which may otherwise seep through the seal around the perimeterof the dressing leading to the formation of leaks.

In order to ensure that the air channel remains open when a vacuum isapplied to the wound cavity, the transmission layer 2105 must besufficiently strong and non-compliant to resist the force due to thepressure differential. However, if this layer comes into contact withthe relatively delicate cover layer 2140, it can cause the formation ofpin-hole openings in the cover layer 2140 which allow air to leak intothe wound cavity. This may be a particular problem when a switchabletype polyurethane film is used that becomes weaker when wet. Theabsorbent layer 2110 is generally formed of a relatively soft,non-abrasive material compared to the material of the transmission layer2105 and therefore does not cause the formation of pin-hole openings inthe cover layer. Thus by providing an absorbent layer 2110 that is ofgreater area than the transmission layer 2105 and that overlaps theedges of the transmission layer 2105, contact between the transmissionlayer and the cover layer is prevented, avoiding the formation ofpin-hole openings in the cover layer 2140.

The absorbent layer 2110 is positioned in fluid contact with the coverlayer 2140. As the absorbent layer absorbs wound exudate, the exudate isdrawn towards the cover layer 2140, bringing the water component of theexudate into contact with the moisture vapor permeable cover layer. Thiswater component is drawn into the cover layer itself and then evaporatesfrom the top surface of the dressing. In this way, the water content ofthe wound exudate can be transpired from the dressing, reducing thevolume of the remaining wound exudate that is to be absorbed by theabsorbent layer 2110, and increasing the time before the dressingbecomes full and must be changed. This process of transpiration occurseven when negative pressure has been applied to the wound cavity, and ithas been found that the pressure difference across the cover layer whena negative pressure is applied to the wound cavity has negligible impacton the moisture vapor transmission rate across the cover layer.

An orifice 2145 is provided in the cover film 2140 to allow a negativepressure to be applied to the dressing 2100. A suction port 2150 issealed to the top of the cover film 2140 over the orifice 2145, andcommunicates negative pressure through the orifice 2145. A length oftubing 2220 may be coupled at a first end to the suction port 2150 andat a second end to a pump unit (not shown) to allow fluids to be pumpedout of the dressing. The port may be adhered and sealed to the coverfilm 2140 using an adhesive such as an acrylic, cyanoacrylate, epoxy, UVcurable or hot melt adhesive. The port 2150 is formed from a softpolymer, for example a polyethylene, a polyvinyl chloride, a silicone orpolyurethane having a hardness of 30 to 90 on the Shore A scale.

An aperture or through-hole 2146 is provided in the absorbent layer 2110beneath the orifice 2145 such that the orifice is connected directly tothe transmission layer 2105. This allows the negative pressure appliedto the port 2150 to be communicated to the transmission layer 2105without passing through the absorbent layer 2110. This ensures that thenegative pressure applied to the wound site is not inhibited by theabsorbent layer as it absorbs wound exudates. In other embodiments, noaperture may be provided in the absorbent layer 2110, or alternatively aplurality of apertures underlying the orifice 2145 may be provided.

As shown in FIG. 15A, one embodiment of the wound dressing 2100comprises an aperture 2146 in the absorbent layer 2100 situatedunderneath the port 2150. In use, for example when negative pressure isapplied to the dressing 2100, a wound facing portion of the port 150 maythus come into contact with the transmission layer 2105, which can thusaid in transmitting negative pressure to the wound site even when theabsorbent layer 2110 is filled with wound fluids. Some embodiments mayhave the cover layer 2140 be at least partly adhered to the transmissionlayer 2105. In some embodiments, the aperture 2146 is at least 1-2 mmlarger than the diameter of the wound facing portion of the port 2150,or the orifice 2145.

A filter element 2130 that is impermeable to liquids, but permeable togases is provided to act as a liquid barrier, and to ensure that noliquids are able to escape from the wound dressing. The filter elementmay also function as a bacterial barrier. Typically the pore size is 0.2μm. Suitable materials for the filter material of the filter element2130 include 0.2 micron Gore™ expanded PTFE from the MMT range, PALLVersapore™ 200R, and Donaldson™ TX6628. Larger pore sizes can also beused but these may require a secondary filter layer to ensure fullbioburden containment. As wound fluid contains lipids it is preferable,though not essential, to use an oleophobic filter membrane for example1.0 micron MMT-332 prior to 0.2 micron MMT-323. This prevents the lipidsfrom blocking the hydrophobic filter. The filter element can be attachedor sealed to the port and/or the cover film 2140 over the orifice 2145.For example, the filter element 2130 may be molded into the port 2150,or may be adhered to both the top of the cover layer 2140 and bottom ofthe port 2150 using an adhesive such as, but not limited to, a UV curedadhesive.

It will be understood that other types of material could be used for thefilter element 2130. More generally a microporous membrane can be usedwhich is a thin, flat sheet of polymeric material, this containsbillions of microscopic pores. Depending upon the membrane chosen thesepores can range in size from 0.01 to more than 10 micrometers.Microporous membranes are available in both hydrophilic (waterfiltering) and hydrophobic (water repellent) forms. In some embodimentsof the disclosure, filter element 2130 comprises a support layer and anacrylic co-polymer membrane formed on the support layer. Preferably thewound dressing 2100 according to certain embodiments of the presentdisclosure uses microporous hydrophobic membranes (MHMs). Numerouspolymers may be employed to form MHMs. For example, PTFE, polypropylene,PVDF and acrylic copolymer. All of these optional polymers can betreated in order to obtain specific surface characteristics that can beboth hydrophobic and oleophobic. As such these will repel liquids withlow surface tensions such as multi-vitamin infusions, lipids,surfactants, oils and organic solvents.

MHMs block liquids whilst allowing air to flow through the membranes.They are also highly efficient air filters eliminating potentiallyinfectious aerosols and particles. A single piece of MHM is well knownas an option to replace mechanical valves or vents. Incorporation ofMHMs can thus reduce product assembly costs improving profits andcosts/benefit ratio to a patient.

The filter element 2130 may also include an odor absorbent material, forexample activated charcoal, carbon fiber cloth or Vitec Carbotec-RTQ2003073 foam, or the like. For example, an odor absorbent material mayform a layer of the filter element 2130 or may be sandwiched betweenmicroporous hydrophobic membranes within the filter element.

The filter element 2130 thus enables gas to be exhausted through theorifice 2145. Liquid, particulates and pathogens however are containedin the dressing.

In FIG. 15B, an embodiment of the wound dressing 2100 is illustratedwhich comprises spacer elements 2152, 2153 in conjunction with the port2150 and the filter 2130. With the addition of such spacer elements2152, 2153, the port 2150 and filter 2130 may be supported out of directcontact with the absorbent layer 2110 and/or the transmission layer2105. The absorbent layer 2110 may also act as an additional spacerelement to keep the filter 2130 from contacting the transmission layer2105. Accordingly, with such a configuration contact of the filter 2130with the transmission layer 2105 and wound fluids during use may thus beminimized. As contrasted with the embodiment illustrated in FIG. 15A,the aperture 2146 through the absorbent layer 2110 may not necessarilyneed to be as large or larger than the port 2150, and would thus onlyneed to be large enough such that an air path can be maintained from theport to the transmission layer 2105 when the absorbent layer 2110 issaturated with wound fluids.

In particular for embodiments with a single port 2150 and through hole,it may be preferable for the port 2150 and through hole to be located inan off-center position as illustrated in FIGS. 15A-B and in FIG. 16.Such a location may permit the dressing 2100 to be positioned onto apatient such that the port 2150 is raised in relation to the remainderof the dressing 2100. So positioned, the port 2150 and the filter 2130may be less likely to come into contact with wound fluids that couldprematurely occlude the filter 2130 so as to impair the transmission ofnegative pressure to the wound site.

FIG. 25 shows a plan view of a suction port 2150 according to someembodiments of the disclosure. The suction port comprises a sealingsurface 2152 for sealing the port to a wound dressing, a connectorportion 2154 for connecting the suction port 2150 to a source ofnegative pressure, and a hemispherical body portion 2156 disposedbetween the sealing surface 2152 and the connector portion 2154. Sealingsurface 2152 comprises a flange that provides a substantially flat areato provide a good seal when the port 2150 is sealed to the cover layer2140. Connector portion 2154 is arranged to be coupled to the externalsource of negative pressure via a length of tube 2220.

According to some embodiments, the filter element 2130 forms part of thebacterial barrier over the wound site, and therefore it is importantthat a good seal is formed and maintained around the filter element.However, it has been determined that a seal formed by adhering thefilter element 2130 to the cover layer 2140 is not sufficientlyreliable. This is a particular problem when a moisture vapor permeablecover layer is used, as the water vapor transpiring from the cover layer2140 can affect the adhesive, leading to breach of the seal between thefilter element and the cover layer. Thus, according to some embodimentsof the disclosure an alternative arrangement for sealing the filterelement 2130 to stop liquid from entering the connector portion 2154 isemployed.

FIG. 26 illustrates a cross section through the suction port 2150 ofFIG. 25 according to some embodiments of the disclosure, the line A-A inFIG. 25 indicating the location of the cross section. In the suctionport of FIG. 26, the suction port 2150 further comprises filter element2130 arranged within the body portion 2156 of the suction port 2150. Aseal between the suction port 2150 and the filter element 2130 isachieved by molding the filter element within the body portion of thesuction port 2150.

FIG. 27 illustrates a cross section through the suction port 2150 ofFIG. 25 according to some embodiments of the disclosure that can be usedwith any dressing embodiment disclosed herein. In the suction port ofFIG. 27, the filter element 2130 is sealed to the sealing surface 2152of the suction port 2150. The filter element may be sealed to thesealing surface using an adhesive or by welding the filter element tothe sealing surface.

By providing the filter element 2130 as part of the suction port 2150,as illustrated in FIGS. 26 and 27, the problems associated with adheringthe filter element to the cover layer 2140 are avoided allowing areliable seal to be provided. Furthermore, providing a sub-assemblyhaving the filter element 2130 included as part of the suction port 2150allows for simpler and more efficient manufacture of the wound dressing2100.

While the suction port 2150 has been described in the context of thewound dressing 2100 of FIG. 15, it will be understood that theembodiments of FIGS. 26 and 27 are applicable to any wound dressing forapplying a negative pressure to a wound disclosed herein or otherwise,wherein wound exudate drawn from the wound is retained within thedressing. According to some embodiments of the disclosure, the suctionport 2150 may be manufactured from a transparent material in order toallow a visual check to be made by a user for the ingress of woundexudate into the suction port 2150.

The wound dressing 2100 and its methods of manufacture and use asdescribed herein may also incorporate features, configurations andmaterials described in the following patents and patent applicationsthat are all incorporated by reference in their entireties herein: U.S.Pat. Nos. 7,524,315, 7,708,724, and 7,909,805; U.S. Patent ApplicationPublication Nos. 2005/0261642, 2007/0167926, 2009/0012483, 2009/0254054,2010/0160879, 2010/0160880, 2010/0174251, 2010/0274207, 2010/0298793,2011/0009838, 2011/0028918, 2011/0054421, and 2011/0054423; as well asU.S. application Ser. No. 12/941,390, filed Nov. 8, 2010, Ser. No.29/389,782, filed Apr. 15, 2011, and Ser. No. 29/389,783, filed Apr. 15,2011. From these incorporated by reference patents and patentapplications, features, configurations, materials and methods ofmanufacture or use for similar components to those described in thepresent disclosure may be substituted, added or implemented intoembodiments of the present application.

In operation the wound dressing 2100 is sealed over a wound site forminga wound cavity. A pump unit (illustrated in FIG. 42 and described infurther detail below) applies a negative pressure at a connectionportion 2154 of the port 2150 which is communicated through the orifice2145 to the transmission layer 2105. Fluid is drawn towards the orificethrough the wound dressing from a wound site below the wound contactlayer 2102. The fluid moves towards the orifice through the transmissionlayer 2105. As the fluid is drawn through the transmission layer 2105wound exudate is absorbed into the absorbent layer 2110.

Turning to FIG. 16 which illustrates a wound dressing 2100 in accordancewith an embodiment of the present disclosure one can see the uppersurface of the cover layer 2140 which extends outwardly away from acentre of the dressing into a border region 2200 surrounding a centralraised region 2201 overlying the transmission layer 2105 and theabsorbent layer 2110. As indicated in FIG. 16 the general shape of thewound dressing is rectangular with rounded corner regions 2202. It willbe appreciated that wound dressings according to other embodiments ofthe present disclosure can be shaped differently such as square,circular or elliptical dressings, or the like.

The wound dressing 2100 may be sized as necessary for the size and typeof wound it will be used in. In some embodiments, the wound dressing2100 may measure between 20 and 40 cm on its long axis, and between 10to 25 cm on its short axis. For example, dressings may be provided insizes of 10×20 cm, 10×30 cm, 10×40 cm, 15×20 cm, and 15×30 cm. In someembodiments, the wound dressing 2100 may be a square-shaped dressingwith sides measuring between 15 and 25 cm (e.g., 15×15 cm, 20×20 cm and25×25 cm). The absorbent layer 2110 may have a smaller area than theoverall dressing, and in some embodiments may have a length and widththat are both about 3 to 10 cm shorter, more preferably about 5 cmshorter, than that of the overall dressing 2100. In somerectangular-shape embodiments, the absorbent layer 2110 may measurebetween 10 and 35 cm on its long axis, and between 5 and 10 cm on itsshort axis. For example, absorbent layers may be provided in sizes of5.6×15 cm or 5×10 cm (for 10×20 cm dressings), 5.6×25 cm or 5×20 cm (for10×30 cm dressings), 5.6×35 cm or 5×30 cm (for 10×40 cm dressings),10×15 cm (for 15×20 cm dressings), and 10×25 cm (for 15×30 cmdressings). In some square-shape embodiments, the absorbent layer 2110may have sides that are between 10 and 20 cm in length (e.g., 10×10 cmfor a 15×15 cm dressing, 15×15 cm for a 20×20 cm dressing, or 20×20 cmfor a 25×25 cm dressing). The transmission layer 2105 is preferablysmaller than the absorbent layer, and in some embodiments may have alength and width that are both about 0.5 to 2 cm shorter, morepreferably about 1 cm shorter, than that of the absorbent layer. In somerectangular-shape embodiments, the transmission layer may measurebetween 9 and 34 cm on its long axis and between 3 and 5 cm on its shortaxis. For example, transmission layers may be provided in sizes of4.6×14 cm or 4×9 cm (for 10×20 cm dressings), 4.6×24 cm or 4×19 cm (for10×30 cm dressings), 4.6×34 cm or 4×29 cm (for 10×40 cm dressings), 9×14cm (for 15×20 cm dressings), and 9×24 cm (for 15×30 cm dressings). Insome square-shape embodiments, the transmission layer may have sidesthat are between 9 and 19 cm in length (e.g., 9×9 cm for a 15×15 cmdressing, 14×14 cm for a 20×20 cm dressing, or 19×19 cm for a 25×25 cmdressing).

It will be understood that according to embodiments of the presentdisclosure the wound contact layer is optional. This layer is, if used,porous to water and faces an underlying wound site. A transmission layer2105 such as an open celled foam, or a knitted or woven spacer fabric isused to distribute gas and fluid removal such that all areas of a woundare subjected to equal pressure. The cover layer together with thefilter layer forms a substantially liquid tight seal over the wound.Thus when a negative pressure is applied to the port 2150 the negativepressure is communicated to the wound cavity below the cover layer. Thisnegative pressure is thus experienced at the target wound site. Fluidincluding air and wound exudate is drawn through the wound contact layerand transmission layer 2105. The wound exudate drawn through the lowerlayers of the wound dressing is dissipated and absorbed into theabsorbent layer 2110 where it is collected and stored. Air and moisturevapor is drawn upwards through the wound dressing through the filterlayer and out of the dressing through the suction port. A portion of thewater content of the wound exudate is drawn through the absorbent layerand into the cover layer 2140 and then evaporates from the surface ofthe dressing.

As discussed above, when a negative pressure is applied to a wounddressing sealed over a wound site, in some dressing embodimentsdisclosed herein, fluids including wound exudate are drawn from thewound site and through the transmission layer 2105 toward the orifice2145. Wound exudate is then drawn into the absorbent layer 2110 where itis absorbed. However, some wound exudate may not be absorbed and maymove to the orifice 2145. Filter element 2130 provides a barrier thatstops any liquid in the wound exudate from entering the connectionportion 2154 of the suction port 2150. Therefore, unabsorbed woundexudate may collect underneath the filter element 2130. If sufficientwound exudate collects at the filter element, a layer of liquid willform across the surface of filter element 2130 and the filter elementwill become blocked as the liquid cannot pass through the filter element2130 and gases will be stopped from reaching the filter element by theliquid layer. Once the filter element becomes blocked, negative pressurecan no longer be communicated to the wound site, and the wound dressingmust be changed for a fresh dressing, even though the total capacity ofthe absorbent layer has not been reached.

In a preferred embodiment, the port 2150, along with any aperture 2146in the absorbing layer 2110 situated below it, generally aligns with themid-longitudinal axis A-A illustrated in FIG. 16. Preferably, the port2150 and any such aperture 2146 are situated closer to one end of thedressing, contrasted with a central position. In some embodiments, theport may be located at a corner of the dressing 2100, which again can beany dressing embodiment disclosed herein including without limitationdressing embodiment 100. For example, in some rectangular embodiments,the port 2150 may be located between 4 and 6 cm from the edge of thedressing, with the aperture 146 located 2 to 3 cm from the edge of theabsorbent layer. In some square embodiments, the port 2150 may belocated between 5 to 8 cm from the corner of the dressing, with theaperture 2146 located 3 to 5 cm from the corner of the absorbent layer.

Certain orientations of the wound dressing may increase the likelihoodof the filter element 130 becoming blocked in this way, as the movementof the wound exudate through the transmission layer may be aided by theeffect of gravity. Thus, if due to the orientation of the wound site andwound dressing, gravity acts to increase the rate at which wound exudateis drawn towards the orifice 2145, the filter may become blocked withwound exudate more quickly. Thus, the wound dressing would have to bechanged more frequently and before the absorbent capacity of theabsorbent layer 2110 has been reached.

In order to avoid the premature blocking of the wound dressing 2100 bywound exudate drawn towards the orifice 2145 some embodiments of thedisclosure include at least one element configured to reduce the rate atwhich wound exudate moves towards the orifice 2145. The at least oneelement may increase the amount of exudate that is absorbed into theabsorbent layer before reaching the orifice 2145 and/or may force thewound exudate to follow a longer path through the dressing beforereaching the orifice 2145, thereby increasing the time before the wounddressing becomes blocked.

FIG. 17 shows a plan view of a wound dressing including baffle elementsthat reduce the rate at which wound exudate moves towards the orificeaccording to one embodiment of the disclosure. The wound dressingillustrated in FIG. 17 is similar to that shown in FIGS. 15 and 16, butincludes a number of baffle elements 2310 disposed across the centralraised region 2201. The baffle elements 2310 form barriers in thecentral region of the dressing, which arrest the movement of woundexudate towards the orifice.

Embodiments of baffle elements that may be used in the wound dressingdescribed herein are preferably at least partly flexible, so as topermit the wound dressing to flex and conform with the skin of thepatient surrounding the wound site. When so present in the wounddressing, the baffle elements are preferably constructed so as to atleast partially prevent liquid from flowing directly to the wounddressing port or orifice and its associated filter, if so provided. Thebaffle elements thus increase the distance that liquids may require toreach the port, which may help in absorbing these fluids into theabsorbent or superabsorbent material of the wound dressing.

According to some embodiments of the disclosure, the baffle element maycomprise a sealing region in which the absorbent layer 2110 andtransmission layer 2105 are absent and cover layer 2140 is sealed to thewound contact layer 2101. Thus, the baffle element presents a barrier tothe motion of the wound exudate, which must therefore follow a path thatavoids the baffle element. Thus the time taken for the wound exudate toreach the orifice is increased.

In some embodiments, the baffle elements may be an insert of asubstantially non-porous material, for example a closed-cellpolyethylene foam, placed inside the dressing. In some cases, it may bepreferable to place such an inserted baffle element in a sealing regionwhere one or more of the absorbent layer 2110 and/or transmission layer2105 are absent. A sealant, for example a viscous curing sealant such asa silicone sealant, could be placed or injected as a thin strip so as toform a baffle element that is substantially liquid impermeable. Such abaffle element could be placed or injected into a region of thetransmission layer 2105 and/or absorbent layer 2110, or also a sealingregion where the absorbent layer 2110 and/or transmission layer 2105 areabsent.

FIG. 20 illustrates a wound dressing, which can be any embodiment of awound dressing disclosed herein, including a baffle element according toa further embodiment of the disclosure. A single baffle element 2610provides a cup shaped barrier between the bulk of the absorbent layer2110 and the orifice 2145. Thus wound exudate that is initially drawnfrom the wound site within the region defined by the baffle element2610, must follow a path around the outside of the cup shaped barrier toreach the orifice 2145. As will be recognized, the baffle element 2610reduces the effect of gravity on reducing the time taken for the woundexudate to move to the orifice 2145, as for most orientations of thewound dressing at least a part of the path taken by the wound exudatewill be against the force of gravity.

The embodiments of FIGS. 17 and 20 have been described with respect to awound dressing having a structure as shown in FIG. 15. However, it willbe understood that the baffle elements could equally be applied to awound dressing in which the transmission layer 2105 was absent.

FIG. 18 shows a plan view of a wound dressing including the at least oneelement according to one embodiment of the disclosure in which a numberof baffle elements 2410 are provided that extend across the width of thecentral region 2201 of the wound dressing, with further baffle elements2412 formed in a semi-circular path around the orifice 2145.

FIG. 19 illustrates the configuration of baffle elements 2410 accordingto some embodiments of the disclosure. The baffle element comprises achannel of absorbent material 2510 underlying the transmission layer2105. A channel in the absorbent layer 2110 is located over the baffleelement 2410 so that the transmission layer is in contact with the coverlayer 2140 in the region of the baffle element 2410. Thus, wound exudatethat is moving along a lower surface of the transmission layer 2105, andhas therefore not been drawn into absorbent layer 2110, will come intocontact with and be absorbed by the channel of absorbent material 2510.

Alternatively, or additionally, baffle elements may comprise one or morechannels provided in the surface of the transmission layer 2105underlying and abutting the absorbent layer 2110. In use, when negativepressure is applied to the wound dressing, the absorbent layer 2110 willbe drawn into the channel. The channel in the transmission layer mayhave a depth substantially equal to the depth of the transmission layer,or may have a depth less than the depth of the transmission layer. Thedimensions of the channel may be chosen to ensure that the channel isfilled by the absorbent layer 2110 when negative pressure is applied tothe wound dressing. According to some embodiments, the channel in thetransmission layer comprises a channel of absorbent material in thetransmission layer 2105.

The baffle elements may be formed into a range of shapes and patterns,for example FIGS. 28A to 28L illustrate wound dressings having a numberof different exemplifying configurations of baffle elements. FIG. 28Aillustrates a linear baffle element in a vertical configuration alignedin the direction of the port or orifice. FIG. 28B illustrates anX-shaped baffle element. FIGS. 28C-E illustrate embodiments of wounddressings with multiple baffle elements, aligned in a generallydiagonal, horizontal, or vertical manner.

FIG. 28F illustrates baffle elements arranged in a six-armed starburstconfiguration, with a center portion left open. FIG. 28G illustrates aW-shaped baffle element on the wound dressing in a position distal tothe port or orifice. In FIG. 28H, an 3-by-3 array of X-shaped baffleelements is provided on the wound dressing, although it will beunderstood that more or less X-shaped baffle elements may be used. FIG.28I shows an embodiment with a plurality of rectangular baffle elements,and wherein one or more baffle elements are located underneath the portin the wound dressing. FIGS. 28J-K illustrate wound dressing embodimentswith longer diagonal and horizontal baffle elements. In FIG. 28L,rectangular baffle elements are present on this embodiment of a wounddressing, wherein the baffle elements are of different sizes.

According to some embodiments of the disclosure, the at least oneelement comprises an array of vias, or troughs, in the transmissionlayer 2105. FIG. 29 illustrates a transmission layer 2105 that isperforated with diamond shaped vias 2210. The vias 2210 are arrangedsuch that no linear pathway exists through the pattern of vias that doesnot intersect with one or more of the vias 2210.

When negative pressure is applied to the wound dressing, the absorbentlayer 2110 is drawn into the vias 2210, increasing the area of theabsorbent layer that comes into contact with wound exudate being drawnthrough the transmission layer 2105. Alternatively, the vias 2210 may befilled with further absorbent material for absorbing wound exudate beingdrawn through the transmission layer 2105. The vias may extend throughthe depth of the transmission layer 2105, or may extend through onlypart of the transmission layer.

Wound exudate moving through the transmission layer 2105 under theinfluence of gravity will fall through the transmission layer in asubstantially linear manner. Any such linear pathways will, at somepoint, intersect with one of the vias 2210, and thus the exudate will bebrought into contact with absorbent material within the vias 2210. Woundexudate coming into contact with absorbent material will be absorbed,stopping the flow of the wound exudate through the transmission layer2105, and reducing the amount of unabsorbed wound exudate that mayotherwise pool around the orifice. It will be appreciated that the viasare not limited to diamond shapes, and that any pattern of vias may beused. Preferably, the vias will be arranged to ensure that all linearpaths through the transmission layer 2105 intersect with at least onevia. The pattern of vias may be chosen to minimize the distance thatwound exudate is able to travel though the transmission layer beforeencountering a via and being absorbed.

FIG. 21 illustrates a wound dressing in accordance with some embodimentsof the disclosure in which the at least one element comprises an airchannel 2710 connecting the central region 2201 of the wound dressing tothe orifice 2145. In the embodiment of FIG. 21, the air channel 2710extends from an edge region of the transmission layer 2105 and connectsthe transmission layer to the orifice 2145.

In use, wound exudate is drawn towards the orifice 2145 by theapplication of negative pressure at the suction port 2150. However, theair channel 2710 present a relatively long serpentine path to befollowed by the wound exudate before it reaches the orifice 2145. Thislong path increases the time that negative pressure can be applied tothe dressing before wound exudate traverses the distance between thetransmission layer and the orifice and blocks the filter element 2130,thereby increasing the time the dressing can be in use before it must bereplaced.

FIG. 22 illustrates a wound dressing in accordance with one embodimentof the disclosure in which the at least one element comprises airchannels 2810 and 2812 connecting the central region 2201 of the wounddressing to the orifice 2145. Channels 2810 and 2812 are coupled to thetransmission layer at substantially opposite corners of the centralregion 2201.

The wound dressing shown in FIG. 22 reduces the effect of gravity on thetime taken for the orifice to become blocked. If the wound dressing isin an orientation in which wound exudate moves under the influence ofgravity towards the edge region of the transmission layer connected toair channel 2810, the effect of gravity will be to move wound exudateaway from the edge region of the transmission layer coupled to airchannel 2812, and vice versa. Thus, the embodiment of FIG. 22 providesalternative air channels for coupling the negative pressure to thetransmission layer such that, should one air channel become blocked aremaining air channel should remain open and able to communicate thenegative pressure to the transmission layer 2105, thereby increasing thetime before negative pressure can no longer be applied to the wounddressing and the dressing must be changed.

Further embodiments of the disclosure may comprise greater numbers ofair channels connecting the transmission layer 2105 to the orifice.

According to some embodiments of the disclosure, two or more orificesmay be provided in the cover layer 2140 for applying the negativepressure to the wound dressing. The two or more orifices can bedistributed across the cover layer 2140 such that if one orifice becomesblocked by wound exudate due to the wound dressing being in a particularorientation, at least one remaining orifice would be expected to remainunblocked. Each orifice is in fluid communication with a wound chamberdefined by the wound dressing, and is therefore able to communicate thenegative pressure to the wound site.

FIG. 23 illustrates a wound dressing in accordance with a furtherembodiment of the disclosure. The wound dressing of FIG. 23 is similarto that of FIGS. 15A-B but includes two orifices 2145 and 2845 providedin the cover layer 2140. A fluid communication passage connects the twoorifices such that a negative pressure applied to one of the orifices iscommunicated to the remaining orifice via the fluid communicationpassage. The orifices 2145, 2845 are located in opposite corner regionsof the cover layer 2140. The fluid communication passage is formed usinga flexible molding 2910 on the upper surface of the cover layer 2140. Itwill be appreciated that the flexible molding may be formed from othersuitable means for example a strip of transmission or open porous foamlayer placed on the cover layer 2140 between the orifices 2145 and 2845and a further film welded or adhered over the strip thus sealing it tothe cover layer and forming a passageway through the foam. A conduit maythen be attached in a known manner to the sealing film for applicationof negative pressure.

In use, the wound dressing having two orifices is sealed over a woundsite to form a wound cavity and an external source of negative pressureis applied to one of the orifices 2145, 2845, and the negative pressurewill be communicated to the remaining orifice via the fluidcommunication passage. Thus, the negative pressure is communicated viathe two orifices 2145, 845 to the transmission layer 2105, and therebyto the wound site. If one of the orifices 2145, 2845 becomes blocked dueto wound exudate collecting at the orifice under the influence ofgravity, the remaining orifice should remain clear, allowing negativepressure to continue to be communicated to the wound site. According tosome embodiments, the transmission layer 2105 may be omitted, and thetwo orifices will communicate the negative pressure to the wound sitevia the absorbent layer 2110.

FIG. 24 illustrates a side view of the fluid communication passage ofthe embodiment of FIG. 23. Molding 2910 is sealed to the top surface ofthe cover layer 2140, and covering orifices 2145 and 2845. Gas permeableliquid impermeable filter elements 2130 are provided at each orifice.The molding 2910 is coupled to an external source of negative pressurevia a tube element 2220.

According to some embodiments, a single filter element may be usedextending underneath the length of the fluid communication passage andthe two orifices. While the above example embodiment has been describedas having two orifices, it will be understood that more than twoorifices could be used, the fluid communication passage allowing thenegative pressure to be communicated between the orifices.

FIG. 30 illustrates an alternative arrangement in which a singleelongate orifice 2350 is provided in the cover layer 2140. First andsecond ends 2355, 2356 of the orifice 2350 are located in oppositecorner regions of the cover layer 2140. A flexible molding 2360 issealed around the orifice 2350 and allows negative pressure to becommunicated through the cover layer 2140 along the length of theorifice 2350. The flexible molding 2360 may be formed by any suitablemeans as described above in relation to flexible molding 2910.

In use, the wound dressing is sealed over a wound site to form a woundcavity and an external source of negative pressure is applied to theorifice. If, due to the orientation of the wound dressing, wound exudatemoves under the influence of gravity to collect around one end 2355 ofthe orifice 2350, a portion of the orifice 2350 near to the end 2355will become blocked. However, a portion of the orifice near to theremaining end 2356 should remain clear, allowing continued applicationof negative pressure to the wound site.

As still further options the dressing can contain anti-microbial e.g.nanocrystalline silver agents on the wound contact layer and/or silversulphur diazine in the absorbent layer. These may be used separately ortogether. These respectively kill micro-organisms in the wound andmicro-organisms in the absorption matrix. As a still further optionother active components, for example, pain suppressants, such asibuprofen, may be included. Also agents which enhance cell activity,such as growth factors or that inhibit enzymes, such as matrixmetalloproteinase inhibitors, such as tissue inhibitors ofmetalloproteinase (TIMPS) or zinc chelators could be utilized. As astill further option odor trapping elements such as activated carbon,cyclodextrine, zeolite or the like may be included in the absorbentlayer or as a still further layer above the filter layer.

FIG. 31 illustrates a first, upper surface 3700 and a further, lowersurface 3702 of a transmission layer 2105 according to an embodiment ofthe present disclosure. In the embodiment illustrated in FIG. 31 fibers3703 of a woven layer extend between the first surface 3700 and thefurther surface 3702. It will be appreciated that according to furtherembodiments of the present disclosure if a foam layer is used as atransmission layer 2105 the connected strands forming the foam will actas spacer elements. As illustrated in FIG. 31 in a relaxed mode ofoperation, that is to say when in use, no negative pressure is appliedto the wound dressing or negative pressure is applied to the wounddressing but no external force acts on the wound dressing then thefibers 3703 extend substantially perpendicular to the upper and lowersurfaces keeping the surfaces in a spaced apart substantially parallelconfiguration.

FIG. 32 illustrates the transmission layer 2105 when an external forceis exerted on the outside of the dressing. The external force can be acompressive force indicated by arrow A and/or a lateral forceillustrated by arrow B in FIG. 32. As indicated either a compressiveforce or a lateral force acts to cause the fibers 3703 to lean to oneside. This causes the upper and lower surfaces to become laterallyoffset with respect to each other as well as causing the thickness ofthe layer to reduce from a separation distance r indicated in FIG. 31 ina relaxed mode of operation to a compression distance c illustrated inFIG. 32. The reduction in thickness effectively provides some “give” inthe dressing even when the dressing is subject to negative pressure. Itwill be appreciated that the forces acting on the dressing may occurthroughout the whole of the surface area of the dressing or only in oneor more particular regions. In such a situation regions of the dressingcan be in a relaxed mode of operation and further regions can be in acompressed mode of operation. As illustrated in FIG. 32 when a force isexerted on the transmission layer the fibers separating the upper andlower surfaces tend to lean to one side sharing a common lean angle.

Throughout this specification reference will be made to a relaxed modeof operation and a forced mode of operation. It is to be understood thatthe relaxed mode of operation corresponds to a natural state of thematerial either when no negative pressure is applied or when negativepressure is applied. In either situation no external force, caused forexample by motion of a patient or an impact is in evidence. By contrasta forced mode of operation occurs when an external force whethercompressive, lateral or other is brought to bear upon the wounddressing. Such forces can cause serious damage/prevent healing or awound.

FIG. 33 illustrates how certain embodiments of the present disclosurecan also operate to offset load forces. As illustrated in FIG. 33 if aforce is exerted over a contact area 3900 in an upper surface 3700 ofthe transmission layer 2105 then this force is transmitted across andthrough the transmission layer and is exerted over a larger dissipationarea 3901 against an underlying wound site. In the case of use of a 3Dknit as a transmission layer this is because the relatively stiff spacerelements provide at least some lateral stiffness to the layer.

FIG. 34 illustrates the transmission layer 2105 and absorbent layer 2110of some embodiments in more detail. The absorbent layer 2110 is locatedproximate to the upper surface 3700 of the transmission layer 2105 andis unbonded thereto according to certain embodiments of the presentdisclosure. When unbonded the absorbent layer 2110 is also able to movelaterally with respect to the underlying transmission layer when alateral or shear force is applied to the wound dressing. Also theabsorbent layer is able to further compress when a compressive forceillustrated in FIG. 35 acts on the wound dressing. As illustrated inFIG. 35 the absorbent layer 2110 decreases in thickness under acompressive force from a non-compressed thickness x illustrated in FIG.34 to a compressed distance y illustrated in FIG. 35. The compressiveforce also acts to offset the upper and lower surfaces of thetransmission layer as described above thus enhancing the “give” of thedressing. The ability for an upper surface 4201 to translate laterallywith respect to a lower surface 4202 of the absorbent layer under alateral or shearing force exerted on the wound dressing is illustratedin more detail in FIG. 36. This lateral motion causes the thickness x ofthe absorbent layer 2110 to reduce and the upper surface and lowersurface of the absorbent layer to be offset with respect to each other.This effect can itself be sufficient to prevent shear forces exerted onthe whole or part of the wound dressing from being transferred to anunderlying wound bed. As can the corresponding effect in thetransmission layer. However a combination enhances the cushioningeffect. If the wound bed comprises a skin graft region the reduction ofshear forces can be particularly advantageous.

It is to be noted that in use the dressing may be used “up-side down”,at an angle or vertical. References to upper and lower are thus used forexplanation purposes only.

FIG. 37 illustrates a cross-section of a portion of an embodiment of adressing shown in FIGS. 15A-16. In particular, FIG. 37 illustrates amagnified view of the wound contact layer 2102 which includes a lowersurface 2101 and multiple perforations 2104 formed as through holes. Anupper surface 2104 of the wound contact layer abuts a first layer 2300of the transmission layer 2105. A further, upper, layer 2301 of thetransmission layer 2105 is spaced apart from the first layer. The firstand further layers of the transmission layer are kept apart in a spacedapart relationship by multiple mono-filament fiber spacers 2302 whichact as resilient flexible pillars separating the two layers of thetransmission layer. The upper layer 2301 of the transmission layer isadjacent a lower surface of the absorbent 2110 which, for example, isformed as a pad of fibrous cellulose material interspaced withsuper-absorbent particulate matter.

FIG. 38 illustrates the lower layer of the 3D fabric transmission layerin more detail. The 3D fabric layer 2105 is formed as a lower and upperknitted layer given a loft by the knitted structure. Rows of the knittedstitches may be referred to as a course of stitches. Columns of stitchesmay be referred to as a whale. A single monofilament fiber is knittedinto the 3D fabric to form the multiple separating strands.

As illustrated in FIG. 38 there are apertures or openings formed betweeninterlocked stitches in the lower layer of the transmission layer 2105.In use, wound exudate including liquid and semi-solid e.g. viscousslurry, suspensions of biological debris or the like and solid materialwill pass upwards through the perforations 2104 in the wound contactlayer and through the openings in the inter knitted structure of thefirst layer 2300 of the transmission layer. The openings between theinterconnected stitches have an average open area ranging from around2250 microns to 450 microns. The particular open area in the first layerof the transmission layer will be determined by the materials and methodof manufacture of the lower layer. FIG. 39 illustrates how an open areaof openings in the further layer above the first layer (that is to sayfurther away from the wound) can include openings which have a greateropen area than the openings in the lower layer. In this way as woundexudate which includes semi-solid and solid matter moves from the woundbed at the wound site upwards into the wound dressing any particulatematter which is of a size small enough to pass through the relativesmall openings 2400 in the lower layer will certainly be able to passthrough the larger area openings 2501 in the upper area. This helpsavoid debris in the form of solid material collecting in theinterstitial region between the monofilament fibers between the upperand lower layer. As shown in FIG. 39, the upper layer 2301 may includeopenings 2500 similar to the openings 2400 in the lower layer 2300.However, during the knitting process the upper surface is knitted sothat larger open area openings 2501 are interspersed across the wholesurface of the upper layer. As illustrated in FIG. 39 the larger openarea openings 2501 can have an open range considerably larger (shownbetween 2700 to 800 microns). The lower layer 2300 thus acts to someextent as a filtering layer having openings 2400 which enable gas andliquid to pass freely therethrough but to prevent solid and semi-solidparticulate matter which is too large from passing in to theinterstitial region in the transmission layer 2105. This helps keep aflowpath along the transmission layer open.

By providing openings in an upper layer in the transmission layer whichhave a greater open area than any openings in the lower area build-up ofsolid particulate matter in the interstitial region between the upperand lower layers of the transmission layer is avoided since any solid orsemi-solid matter will flow along the channel and eventually be enabledto pass upwards through the larger openings where the material is takenup by the super-absorber/absorbent material.

The absorbent layer 2110 holds liquid collected during the applicationof negative pressure therapy. By having this layer in fluidcommunication with, and preferably in contact with, the layer of thetransmission layer, the region of the transmission layer 2105 is kept ata moist environment. This helps avoid build-up and crusting of theexudate during use.

FIG. 40 illustrates an alternative material which could be utilized asthe transmission layer in a wound dressing. In particular, FIG. 40illustrates a lower surface of a 3D knit material which may be utilizedas the transmission layer. Openings 2600 are formed in the surface whichenables wound exudate and air to pass from the wound through a woundcontact layer which would be located on the surface shown in FIG. 20 andthrough those openings. FIG. 41 illustrates an upper surface of thematerial shown in FIG. 40 and illustrates how larger openings 2700 maybe formed in the upper surface.

Whilst certain embodiments of the present disclosure have so far beendescribed in which the transmission layer is formed as a 3D knit layer,e.g., two layers spaced apart by a monofilament layer, it will beappreciated that certain embodiments of the present disclosure are notrestricted to the use of such a material. In some embodiments, as analternative to such a 3D knit material one or more layers of a widevariety of materials could be utilized. In each case, according toembodiments of the present disclosure, the openings presented by layersof the transmission layer are wider and wider as one moves away from theside of the dressing which, in use will be located proximate to thewound. In some embodiments, the transmission layer may be provided bymultiple layers of open celled foam. In some embodiments, the foam isreticulated open cell foam. Preferably, the foam is hydrophilic or ableto wick aqueous based fluids. The pore size in each layer is selected sothat in the foam layer most proximate to the wound side in use the poreshave a smallest size. If only one further foam layer is utilized thatincludes pore sizes which are greater than the pore sizes of the firstlayer. This helps avoid solid particulate being trapped in the lowerlayer which thus helps maintain the lower layer in an open configurationin which it is thus able to transmit air throughout the dressing. Incertain embodiments, two, three, four or more foam layers may beincluded. The foam layers may be integrally formed, for example, byselecting a foam having a large pore size and then repeatedly dippingthis to a lesser and lesser extent into material which will clog thepores or alternatively, the transmission layer formed by the multiplefoam layers may be provided by laminating different types of foam in alayered arrangement or by securing such layers of foam in place in aknown manner.

According to certain embodiments of the present disclosure, thetransmission layer is formed by multiple layers of mesh instead of foamor 3D knit materials. For example, fine gauze mesh may be utilized for awound facing side of the transmission layer and a Hessian mesh having alarger pore size may be located on a distal side of the gauze meshfacing away from the wound in use. The one, two, three or more layers ofmesh can be secured together in an appropriate manner, such as beingstitched or adhered together or the like. The resultant mat of fibersprovides a transmittal layer through which air can be transmitted in thedressing but by selecting the opening sizes in the meshes as one movesthrough the dressing away from the wound contact side, the accumulationof solid particulate matter in lower layers can be avoided.

FIG. 42 illustrates an embodiment of a TNP wound treatment comprising awound dressing 2100 in combination with a pump 2800. As stated above,the wound dressing 2100 can be any wound dressing embodiment disclosedherein including without limitation dressing embodiment 100 or have anycombination of features of any number of wound dressing embodimentsdisclosed herein. Here, the dressing 2100 may be placed over a wound asdescribed previously, and a conduit 2220 may then be connected to theport 2150, although in some embodiments the dressing 2100 may beprovided with at least a portion of the conduit 2220 preattached to theport 2150. Preferably, the dressing 2100 is provided as a single articlewith all wound dressing elements (including the port 2150) pre-attachedand integrated into a single unit. The wound dressing 2100 may then beconnected, via the conduit 2220, to a source of negative pressure suchas the pump 2800. The pump 2800 can be miniaturized and portable,although larger conventional pumps may also be used with the dressing2100. In some embodiments, the pump 2800 may be attached or mounted ontoor adjacent the dressing 2100. A connector 2221 may also be provided soas to permit the conduit 2220 leading to the wound dressing 2100 to bedisconnected from the pump, which may be useful for example duringdressing changes.

FIGS. 43A-D illustrate the use of an embodiment of a TNP wound treatmentsystem being used to treat a wound site on a patient. FIG. 43A shows awound site 2190 being cleaned and prepared for treatment. Here, thehealthy skin surrounding the wound site 2190 is preferably cleaned andexcess hair removed or shaved. The wound site 2190 may also be irrigatedwith sterile saline solution if necessary. Optionally, a skin protectantmay be applied to the skin surrounding the wound site 2190. Ifnecessary, a wound packing material, such as foam or gauze, may beplaced in the wound site 2190. This may be preferable if the wound site2190 is a deeper wound.

After the skin surrounding the wound site 2190 is dry, and withreference now to FIG. 43B, the wound dressing 2100 may be positioned andplaced over the wound site 2190. Preferably, the wound dressing 2100 isplaced with the wound contact layer 2102 over and/or in contact with thewound site 2190. In some embodiments, an adhesive layer is provided onthe lower surface 2101 of the wound contact layer 2102, which may insome cases be protected by an optional release layer to be removed priorto placement of the wound dressing 2100 over the wound site 2190.Preferably, the dressing 2100 is positioned such that the port 2150 isin a raised position with respect to the remainder of the dressing 2100so as to avoid fluid pooling around the port. In some embodiments, thedressing 2100 is positioned so that the port 2150 is not directlyoverlying the wound, and is level with or at a higher point than thewound. To help ensure adequate sealing for TNP, the edges of thedressing 2100 are preferably smoothed over to avoid creases or folds.

With reference now to FIG. 43C, the dressing 2100 is connected to thepump 2800. The pump 2800 is configured to apply negative pressure to thewound site via the dressing 2100, and typically through a conduit. Insome embodiments, and as described above in FIG. 42, a connector may beused to join the conduit from the dressing 2100 to the pump 2800. Uponthe application of negative pressure with the pump 2800, the dressing2100 may in some embodiments partially collapse and present a wrinkledappearance as a result of the evacuation of some or all of the airunderneath the dressing 2100. In some embodiments, the pump 2800 may beconfigured to detect if any leaks are present in the dressing 2100, suchas at the interface between the dressing 2100 and the skin surroundingthe wound site 2190. Should a leak be found, such leak is preferablyremedied prior to continuing treatment.

Turning to FIG. 43D, additional fixation strips 2195 may also beattached around the edges of the dressing 2100. Such fixation strips2195 may be advantageous in some situations so as to provide additionalsealing against the skin of the patient surrounding the wound site 2190.For example, the fixation strips 2195 may provide additional sealing forwhen a patient is more mobile. In some cases, the fixation strips 2195may be used prior to activation of the pump 2800, particularly if thedressing 2100 is placed over a difficult to reach or contoured area.

Treatment of the wound site 2190 preferably continues until the woundhas reached a desired level of healing. In some embodiments, it may bedesirable to replace the dressing 2100 after a certain time period haselapsed, or if the dressing is full of wound fluids. During suchchanges, the pump 2800 may be kept, with just the dressing 2100 beingchanged.

With the some embodiments of the present disclosure, a wound dressing isprovided that helps improve patient concordance with instructions foruse, helps improve patients' quality of life, and also helps a clinicianobserve and monitor a patient's wound.

It will be clear to a person skilled in the art that features describedin relation to any of the embodiments described above can be applicableinterchangeably between the different embodiments. The embodimentsdescribed above are examples to illustrate various features of thepresent invention or inventions.

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of them mean “including but notlimited to”, and they are not intended to (and do not) exclude othermoieties, additives, components, integers or steps. Throughout thedescription and claims of this specification, the singular encompassesthe plural unless the context otherwise requires. In particular, wherethe indefinite article is used, the specification is to be understood ascontemplating plurality as well as singularity, unless the contextrequires otherwise.

Features, integers, characteristics, compounds, chemical moieties orgroups described in conjunction with a particular aspect, embodiment orexample of the present disclosure are to be understood to be applicableto any other aspect, embodiment or example described herein unlessincompatible therewith. All of the features disclosed in thisspecification (including any accompanying claims, abstract anddrawings), and/or all of the steps of any method or process sodisclosed, may be combined in any combination, except combinations whereat least some of such features and/or steps are mutually exclusive. Theinvention is not restricted to the details of any foregoing embodiments.The invention extends to any novel one, or any novel combination, of thefeatures disclosed in this specification (including any accompanyingclaims, abstract and drawings), or to any novel one, or any novelcombination, of the steps of any method or process so disclosed.

The readers attention is directed to all papers and documents which arefiled concurrently with or previous to this specification in connectionwith this application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

The invention claimed is:
 1. A method of treating a wound, the methodcomprising: positioning a wound dressing over a wound, the wounddressing comprising: a central region and a radially outer region aroundthe central region, wherein the wound dressing comprises four roundedlobes extending from the central region of the dressing; a wound contactlayer; an absorbent layer for absorbing wound exudate, the absorbentlayer positioned above the wound contact layer; an obscuring element forat least partially obscuring a view of wound exudate absorbed by theabsorbent layer in use, the obscuring element positioned above theabsorbent layer; and a cover layer positioned above the obscuringelement, wherein the obscuring element is positioned between theabsorbent layer and the cover layer at the central region and configuredsuch that a portion of the absorbent layer is viewable under the coverlayer at the radially outer region; sealing the wound dressing to skinaround the wound; and determining whether to change the wound dressingbased at least partly on the wound dressing providing an indication ofthe spread of exudate from the wound into the portion of the absorbentlayer at the radially outer region viewable under the wound cover. 2.The method of claim 1, wherein the obscuring element is a layer thatcovers the central region and has a smaller dimension than the absorbentlayer at the radially outer region.
 3. The method of claim 1, whereinthe obscuring element is a layer that has windows at the radially outerregion.
 4. The method of claim 1, further comprising changing the wounddressing after an amount of exudate is visible under the cover layer atthe radially outer region.
 5. The method of claim 1, further comprising:monitoring the spread of exudate; and providing an electronic indicatorrepresenting the spread of the exudate.
 6. The method of claim 5,wherein the electronic indicator comprises red, amber, and green lightsto indicate the spread of the exudate.
 7. The method of claim 5, whereinthe obscuring element comprises the electronic indicator.
 8. The methodof claim 1, further comprising: determining a percentage of coverage ofthe portion of the absorbent layer with exudate at the radially outerregion viewable under the cover layer; and changing the wound dressingin response to determining that the percentage of coverage exceeds athreshold.
 9. The method of claim 8, wherein the threshold is 50%. 10.The method of claim 1, further comprising: determining a distance of thespread of exudate from an edge of the dressing; and changing the wounddressing in response to determining that the distance exceeds athreshold.
 11. The method of claim 10, wherein the distance is 5 mm. 12.The method of claim 10, wherein the distance is 7 mm.
 13. The method ofclaim 1, further comprising centering the wound dressing over the wound.14. The method of claim 1, further comprising: determining whether thewound dressing has been in use for at least a maximum recommendedduration; and in response to determining that the wound dressing hasbeen in use for the maximum recommended duration, changing the wounddressing.
 15. The method of claim 1, further comprising monitoring thespread of exudate at predetermined intervals.
 16. The method of claim 1,wherein the wound dressing is shaped to include sub-areas, wherein thewound dressing has rotational symmetry, and wherein the sub-areas defineareas of the wound dressing that are formable in different directionswith respect to each other.
 17. The method of claim 1, wherein the wounddressing comprises five or more rounded lobes extending from the centralregion of the dressing.
 18. A method of treating a wound, the methodcomprising: positioning a wound dressing over a wound, the wounddressing comprising: a central region and a radially outer region aroundthe central region, wherein the wound dressing comprises four roundedlobes extending from the central region of the dressing; a wound contactlayer; an absorbent layer for absorbing wound exudate, the absorbentlayer positioned above the wound contact layer; and a cover layerpositioned above the absorbent layer; sealing the wound dressing to skinaround the wound; and absorbing wound exudate within the absorbent layerof the wound dressing.
 19. The method of claim 18, wherein the wounddressing comprises a masking layer that at least partially obscures aview of wound exudate absorbed by the absorbent layer in use, themasking layer positioned between the absorbent layer and the coverlayer.
 20. The method of claim 18, further comprising changing the wounddressing after an amount of exudate is visible under the cover layer atthe radially outer region.
 21. The method of claim 18, wherein the wounddressing comprises five or more rounded lobes extending from the centralregion of the dressing.